Raven et al. 2023 on ankylosaur phylogeny missed the shortest trees and should not have dropped Nodosauridae

A new paper came out analyzing thyreophoran phylogenetics - Raven et al. (2023).  The abstract states "This dataset was analysed using equal- and implied-weights parsimony and Bayesian inference, and further explored using constraint trees and partitioned datasets. Stratigraphical congruence was used to identify a 'preferred tree' and these analyses reveal a novel hypothesis for thyreophoran relationships. The traditional ankylosaurian dichotomy is not supported: instead, four distinct ankylosaur clades are identified, with the long-standing 'traditional' clade Nodosauridae rendered paraphyletic. Ankylosauridae, Panoplosauridae, Polacanthidae and Struthiosauridae have distinct morphotypes..."

Four distinct ankylosaur clades with distinct morphotypes?

It sounds intriguing, but then Polacanthidae as a separate clade or grade has been a viable hypothesis since 1998, so I guess it's the paraphyly of Panoplosaurus and Struthiosaurus versus Ankylosaurus that is new?  Looking back, that was ambiguous in Vickaryous et al. (2001),  Osi (2005) and Parsons and Parsons (2009) but rejected by Osi and Makadi (2009), Thompson et al. (2012) and Arbour et al. (2016), thus it would be surprising to someone like myself who doesn't specialize in ornithischians so is not all that familiar with character support and such.

So let's see what Raven et al. found.  They did five basic analyses (A-D with [edited thanks to David Marjanovic's comment] progressively more different assumed weighting- unweighted, then k = 3, 8 and 12; E as a Bayesian attempt) then some constraint analyses and ones using only certain parts of the skeleton.  I'm going to ignore the latter as I don't think anyone considers "cranial only", "postcranial only" or "armor only" to give better results in Mesozoic dinosaur phylogenetics.  In any case, the first analysis (Analysis A) was equal weights, which is the standard for Mesozoic dinosaur analyses and how basically every prior ankylosaur analysis was run.  As an aside, statements like "The strict consensus tree (Supplementary material, Fig. S75) shows a lack of resolution in Stegosauria" .... "and Ankylosauria is found in an unresolved polytomy with most stegosaur taxa" just means you haven't pruned enough taxa a posteriori to see the underlying structure.  It's annoying the authors never look into what that structure is and leave the tree looking artificially uncertain.  But the main result in Ankylosauria is... "There are two clades within Ankylosauria (Ankylosauridae + Nodosauridae)"!  So the expected usual result.  Hmm.  But what about their novel hypothesis of three nodosaur clades at least? 

They state "Within Nodosauridae, there are three groupings of taxa: 'polacanthid' ankylosaurs, but excluding Polacanthus; a 'panoplosaurid' group typified by Edmontonia and Panoplosaurus; and a 'struthiosaurid' group typified by Struthiosaurus and Hungarosaurus."  But are there?  Just look at the cladogram above (which is only in the supp info). 'Polacanthidae excluding Polacanthus' is Texasetes, the then-unnamed Patagopelta, Sauropelta, Hylaeosaurus, Hoplitosaurus, Tatankacephalus, an undescribed Wessex specimen, Zhejiangosaurus, Antarctopelta and Dongyangopelta.  Besides Hoplitosaurus and Hylaeosaurus (which I don't know has ever been recovered as a polacanthid, just guessed to be there), I don't think any of these have been associated with Polacanthidae/inae before.  The 'core' polacanthids besides Polacanthus itself are Gastonia, Mymoorapelta and maybe Gargoyleosaurus, so I wouldn't say this clade is reflective of Polacanthidae in any sense.  But okay you say, maybe it's not Polacanthidae, but surely the analyses (PLURAL as in the abstract) revealed a 'distinct morphotype' for this Sauropelta-Hylaeosaurus clade of nodosaurs?  Looking at their "preferred tree" (Analysis B, k=3) only Patagopelta, Texasetes, Hoplitosaurus and Hylaeosaurus are shared between 'polacanthid' clades, with five new taxa in there compared to Analysis A.  And in Analysis C (k=8) only Hoplitosaurus and Texasetes are shared (with seven new taxa), while by Analysis D (k=12) all these taxa are scattered to the wind and there's no equivalent at all.  And Analysis E (Bayesian) is one huge polytomy for ankylosaurs.  So I would suggest their published results do not support any clade like this that is robust when analyzed under different criteria.

But what about Panoplosauridae and Struthiosauridae?  First of all, just as there are nine 'nodosaurs' that fall outside the Nodosauridae+ Ankylosauridae split, there are one to five nodosaurids that don't fall into either the panoplosaur or struthiosaur clades.  We can't tell how many because Raven et al. do not prune a posteriori to try to resolve any polytomies.  But the panoplosaur group is Dracopelta, Aletopelta, both Edmontonia species, Denversaurus and of course Panoplosaurus.  The latter three have always been grouped together, but the first two would be interesting if they actually were panoplosaurs.  The 'preferred tree' (k=3) takes away Aletopelta and adds Nodosaurus, Anoplosaurus and Tianchisaurus; Analysis C (k=8) has the core three genera plus Dracopelta and Anoplosaurus, while Analysis D (k=12) has everything in A plus Anoplosaurus and Nodosaurus.  So Dracopelta is always a panoplosaur and Anoplosaurus is with any unequal weighting, which are the first surprising, new and widely supported nodosaur placements in this study.  Yet neither is touted in the text or written up with character support, and honestly the idea of Albian-Cenomanian English Anoplosaurus and especially Jurassic European Dracopelta breaking up not just Campanian-Maastrichtian North American Panoplosaurus+Edmontonia, but the genus Edmontonia itself(!) just seems unlikely.  And indeed, a fairly complete Dracopelta specimen (Russo and Mateus, 2023) was recently discovered, and the authors found "D. zbyszewskii [was] consistently recovered as sister taxa of G[argoyleosaurus] parkpinorum, from the Upper Jurassic of Morrison Formation, USA, in a basal ankylosaur group that also includes the other Morrison Formation ankylosaur, M[ymoorapelta] maysi," which matches temporally so much better.

As for Struthiosauridae, the unweighted tree would have this include Borealopelta, Minmi, Niobrarasaurus, Polacanthus, Europelta, Liaoningosaurus, Stegopelta, the Paw Paw Formation juvenile (* see below), Hungarosaurus and all three Struthiosaurus species (not monophyletic, at least Tianchisaurus is closer to S. transylvanicus than to S. austriacus or S. languedocensis).  The 'preferred tree' (k=3) keeps only Struthiosaurus, Hungarosaurus, the Paw Paw juvenile and Europelta, and adds Silvisaurus and Taohelong.  Analysis C (k=8) drops the latter two but adds Tianchisaurus back, and Analysis D (k=12) keeps the two and everything from the unweighted tree plus adds Invictarx and Hoplitosaurus.  So far from dividing the 'distinct morphotypes' of Polacanthidae and Struthiosauridae, two of five trees have Polacanthus as a struthiosaur.  Here the results are besides the Santonian-Maastrichtian Central European Struthiosaurus/Hungarosaurus, the struthiosaur clade includes Europelta (as guessed by its describers), the Early Cretaceous American Paw Paw juvenile and usually the Jurassic Chinese Tianchisaurus.  Yet the authors never mention the Paw Paw juvenile ever falling out here, and have Tianchisaurus as a panoplosaurid because Analysis B is the one time it wasn't the sister to Struthiosaurus transylvanicus.  In fact, the authors falsely* state the Paw Paw juvenile is usually a basal ankylosaur and Figure 2 incorrectly* shows it being one in a supposed "Agreement subtree of the three implied weighing analyses (analyses B–D)."  How did this happen?! ...

(*) I figured it out- the trees in the supp info switched Pawpawsaurus and the Paw Paw juvenile, while figures 1-3 in the paper are correct.  So actually their trees have Pawpawsaurus as the struthiosaur sister to Hungarosaurus, which has the same chronostratigraphic issues as the juvenile from the same formation.

If we go back to the big picture in Ankylosauria, the unweighted Analysis A gave us a large Nodosauridae with some mostly Jurassic taxa basal to the Nodo-Ankylo split, and a few 'nodosaurs' (Kunbarrasaurus, Peloroplites, Liaoningosaurus) as basal ankylosaurids.  'Preferred' Analysis B (k=3) has polacanthids basal to the split, then panoplosaurs and struthiosaurs sister to each other, so again is pretty standard.  Analysis C (k=8) has struthiosaurs, panoplosaurs and polacanthids successively closer to ankylosaurids, so at least that has the paraphyletic nodosaurs the article touts.  Finally, Analysis D (k=12) has struthiosaurs further from ankylosaurids than panoplosaurs while polacanthids cease to really exist (their internal specifier Gastonia [see below] is an ankylosaurid but Polacanthus and Hoplitosaurus are struthiosaurs).

So I guess if I had a takeaway from their published results (**, see below), it would be that Dracopelta (probably incorrectly) and usually Anoplosaurus are panoplosaurs; Europelta, Pawpawsaurus and usually Tianchisaurus (not even supported by the authors) are struthiosaurs; polacanthids are not strongly supported in any form; and nodosaurs become increasingly paraphyletic with more weighting greater values of k (corrected again thanks to David Marjanovic's comment), although you need to get to k=8 for anything really novel.  And it's the weighting that is one of my major issues with this paper, because why is k=3 the preferred tree?  Because "The stratigraphically most congruent topology, as identified by the four stratigraphical congruence metrics (SCI, RCI, MSM
and GER), was Analysis B, and so this was selected as the 'preferred tree'."  But if you look at their Table 2 (below), the Bayesian analysis destroys the others at SCI (0.929 vs. 0.438-0.500), but we never get to know what those results are since the authors just leave it as a huge polytomy without further analysis.  And in the other three, Analysis B is 16.954, .023 and .005 better respectively, which seems increasingly less important.  I have no idea how any of these measures work, but it seems incredibly arbitrary to say whichever k value is best in a majority of four methods wins, ignoring anything quantitative.

(**) Raven et al. didn't find the shortest trees

But now we get to the part where I reveal nothing I said above matters, because Raven et al. didn't get the shortest trees.  EDIT BELOW Not even close.  Instead of producing "eight MPTs with lengths of 1508 steps", their unweighted matrix Analysis A results in >99999 MPTs of 1464 steps.  Here's the real strict consensus with 13 taxa pruned a posteriori for resolution-

As you can see, it's not the same as Raven et al.'s Figure S75.  For one, stegosaurs resolve, although weirdly with Toujiangosaurus+Paranthodon as ankylosaurs.  For two it's WAY less resolved in Ankylosauria.  All those taxa from Zhejiangosaurus through Ahshishlepelta never form a consistent clade with each other or the four ankylosaur clades, and if you prune all nine genera, struthiosaurs, ankylosaurids and 'panoplosaurs'+polacanthids are still a trichotomy.  So their matrix doesn't actually show how these taxa relate (besides polacanthids being sister to 'panoplosaurs').  Isn't it ironic though that we do get Raven et al.'s three nodosaur clades including a classic Polacanthinae that includes Gastonia, Gargoyleosaurus and Mymoorapelta in addition to Jurassic Sarcolestes (and basally some parankylosaurs, but the paper was too late to include Stegouros)?  Struthiosauridae is only Struthiosaurus spp. plus Hungarosaurus and Tianchisaurus, which again is funny because the latter was not included in the clade by the authors due only to their Analysis B.  'Panoplosauridae' includes a lot more taxa, and yes those basal ones don't clade with each other or successively to the core group no matter how many are pruned, so that's another real polytomy.  As for the pruned taxa-

Mongolostegus can at least be sister to Chungkingosaurus or a struthiosaurine.
Adratiklit is part of the Dacentrurus+Stegosaurus clade.
Anodontosaurus and Scolosaurus are part of the Euoplocephalus+Pinacosaurus clade.
Tarchia kielanae is part of the Ankylosaurus+Euoplocephalus clade.
Acantholipan can be a 'panoplosaur', a struthiosaurine or outside (by which I mean a taxon closer to Ankylosaurus than Toujiangosaurus but not part of the struthiosaur, ankylosaurid or polacanthid+'panoplosaur' clades shown, though it could be e.g. sister to any of these clades and thus fall under their definitions).
Borealopelta can be a struthiosaurine, a 'panoplosaur' or outside(?).
Europelta can be a struthiosaurine or outside.
Invictarx can be a struthiosaurine, a 'panoplosaur' or outside.
Nodosaurus is always closer to Panoplosaurus than Silvisaurus.
Patagopelta can be a basal 'panoplosaur' or outside.
Pawpawsaurus can be a struthiosaurine or 'panoplosaur'.
Stegopelta can be a struthiosaurine or outside.

EDIT ADDED 5-21: Thanks to Andrea Cau in the comments for pointing out Raven et al. didn't include their character ordering settings in their txt file.  I wrongly assumed it would have a ccode line or a ctype line below the matrix but never scrolled all the way down.  I should have been suspicious when I had to manually choose the outgroup instead of them just making Lesothosaurus the first taxon in the matrix.  On the one hand, my bad.  On the other hand, it's surely best practice to not force your readers to modify the settings of the file you provided to the journal.

In any case, it still doesn't matter because Raven et al. STILL didn't find the shortest trees.  Instead of producing "eight MPTs with lengths of 1508 steps", their unweighted matrix Analysis A results in >99999 MPTs of 1506 steps.  Here's the real REAL strict consensus with 13 taxa pruned a posteriori for resolution-



Two steps doesn't sound like much, but it's enough to make 'polacanthids' a grade of basal ankylosaurids, make struthiosaurines nodosaurids as in traditional phylogenies and kick Dracopelta and Anoplosaurus out of panoplosaurs.  And yes, Nodosaurus is still closer to Panoplosaurus than Silvisaurus or Struthiosaurus.  The toplogy still has Tuojiangosaurus+Paranthodon as ankylosaurs and a struthiosaur Tianchisaurus too.

What are these clades named?

Raven et al. propose new definitions for their three nodosaur families-

"Panoplosauridae
All ankylosaurs more closely related to Panoplosaurus than to Ankylosaurus, Struthiosaurus austriacus or Gastonia burgei

Polacanthidae
All ankylosaurs more closely related to Gastonia burgei than to Ankylosaurus, Panoplosaurus or Struthiosaurus austriacus

Struthiosauridae
All ankylosaurs more closely related to Struthiosaurus austriacus than to Ankylosaurus, Panoplosaurus or Gastonia burgei"

Tim Williams has already rightfully complained on the DML that their Polacanthidae definition needs to use Polacanthus foxii.  Why is this so hard in 2023?!  Do Arbour and the "three anonymous referees" not know the basics of phylogenetic nomenclature?  PhyloCode Article 11.10 states "when a clade name is converted from a preexisting name that is typified under a rank-based code or is a new or converted name derived from the stem of a typified name, the definition of the clade name must use the type species of that preexisting typified name or of the genus name from which it is derived (or the type specimen of that species) as an internal specifier."  We've been complaining about it since Sereno 24 years ago, surely every dinosaur worker knows by now.

Another obvious issue is that Nodosauridae has priority over Panoplosauridae, Struthiosauridae and Polacanthidae, so where's Nodosauridae?  Raven et al. explain "Nodosaurus is recovered outside of
Panoplosauridae in Analyses A and C, further suggesting that application of the name Nodosauridae would add confusion."  But as noted above, Nodosaurus is actually always a 'panoplosaur' when Analysis A is run correctly, and the fact it's supposedly an ankylosaurid sister to Dyoplosaurus when k=8 (fig. S77) should be close to worthless in my view.  Unless one of the authors wants to claim whatever character is being weighed eight times more than others could realistically mean this Cenomanian taxon is really within a Campanian species complex that are so similar they were all placed under Euoplocephalus tutus until recently?  Also, Polacanthus doesn't fall in their definition of Polacanthidae in two of their four trees, so why is that still allowed as a family name?

In any case, the clades have already been officially defined with PhyloCode registrations, by Madzia et al. (2021).  Raven et al. was "Received 7 February 2022", so I don't know why Arbour (a coauthor on Madzia et al.!) or the reviewers would let that stay in the paper.  Reading through, Raven et al. actually cite Madzia et al. and state "the underlying philosophy of the latter study is based on the PhyloCode (de Queiroz & Cantino, 2020) and offers an alternative hypothesis to our study, which is framed by the traditional principles of the International Commission on Zoological Nomenclature (1999), and so is not discussed further." Hahahaha  I hate to tell you guys, but defining clades based on phylogenetic relationships has nothing to do with the ICZN.  And if you were following the "traditional principles" of the 1999 ICZN, you couldn't just throw Nodosauridae away while stating "In the 'preferred' tree Panoplosauridae consists of ... Nodosaurus" and "A clade of generally Late Cretaceous North American taxa is also recovered here and named Panoplosauridae. As well as Denversaurus, Edmontonia spp., Nodosaurus and Panoplosaurus..."  Instead you would follow ICZN Article 65.2.3 - "by the discovery that the type genus was, when established, based on a type species then misidentified, the author may fix as the type species a nominal species as prescribed in Article 70.3. If the threat cannot be overcome by the fixation of a type species under the provisions of Article 70.3 the case is to be referred to the Commission for a ruling."  But that's not happening because I bet they think it's unlikely Nodosaurus is outside Nodosauridae.  "... is not discussed further" is short here for "... we know it makes no sense but we don't want to address it."

And Madzia et al. do a good job because they actually follow the rules.  Except in Raven et al.'s topology Stegosauridae ends up being the Chungkingosaurus+Eurypoda clade due to Huayangosaurus' weird position outside Eurypoda (which supposedly happens in the Bayesian analysis too), which could be saved by adding Ankylosaurus magniventris as an external specifier.  Similarly, Struthiosaurini might benefit from an Ankylosaurus magniventris external specifier due to the polytomy.  So here's the actual unweighted results with official clade names-

1. Ankylosauria; 2. Ankylosauridae; 3. Ankylosaurinae; 4. Ankylosaurini; 5. Eurypoda; 6. Huayangosauridae; 7. Nodosauridae; 8. Nodosaurinae; 9. Polacanthinae; 10. Shamosaurinae; 11. Stegosauria; 12. Struthiosaurini. Note due to Nodosaurus' possible positions, Panoplosaurini cannot be placed precisely in this tree.

For a couple final thoughts, Raven et al.'s definition for Shamosaurinae ("All ankylosaurid ankylosaurs more closely related to Shamosaurus than to Ankylosaurus") is better than the official definition ("max ∇ (Gobisaurus domoculus Vickaryous et al., 2001 & Shamosaurus scutatus Tumanova, 1983 ~ Ankylosaurus magniventris Brown, 1908") because Gobisaurus has no reason to be involved.  Also, Kirkland et al.'s (2013) definition of Struthiosaurinae is just horrible- "the most inclusive clade containing Europelta but not Cedarpelta, Peloroplites, Sauropelta or Edmontonia."  Doesn't separate it from ankylosaurids or polacanthines, includes Cedarpelta and Peloroplites which have no agreed upon positions or competing family-level names, AND doesn't use Struthiosaurus austriacus as the internal specifier.  Oof.  And why have "Bayesian analysis' as a keyword in Raven et al. (2023), run the Bayesian analysis for a week, mention it in the abstract, and despite having by far the best SCI score just leave it as a huge ankylosaur polytomy that has no effect on its conclusions?

So does nobody test run these analyses before they are accepted?

I began this post just planning to harp on peoples' seeming inability to learn Phylocode Article 11.10, but it ended up so much worse.  It's not like I searched and scoured to find a better cladogram in the data, TNT popped it out in (checking) under 30 seconds.  And then there's the Pawpawsaurus vs. Paw Paw juvenile switch that made the supp info wrong that I guess nobody noticed?  I'm just a person looking over the article on a random Saturday, not a journal editor or a professional whose job description woefully includes peer reviewing.  And sure mistakes are made, maybe the authors are anti-Phylocode despite proposing phylogenetic definitions (what organization is going to lend yours any validity?) and maybe nobody on the team knows how to use TNT, but I also just found the basic results quote from the top of my post to be misleading.  The published results did NOT show that nodosaurs fall into three "distinct morphotypes" past the standard Latest Cretaceous Central European struthiosaurines and North American panoplosaurins except for maybe 2-5 additional genera, NOR that they were more paraphyletic than normally thought and basically nothing was shown about polacanthines, with the statement "'polacanthid' ankylosaurs, but excluding Polacanthus" in Analysis A being plain wrong.  My best guess is that after getting pretty inconclusive results the team went with the "Nodosauridae isn't real" gimmick despite the hypocrisy in keeping Polacanthidae.  I think the real message of the analysis (assuming accurate scorings) is that ankylosaurs need a lot more characters analyzed to determine their basal relationships. the basic topology from twenty years ago is still most parsimonious.


References- Vickaryous, Russell, Currie and Zhao, 2001. A new ankylosaurid (Dinosauria:
Ankylosauria) from the Lower Cretaceous of China, with comments on ankylosaurian relationships. Canadian Journal of Earth Sciences. 38(2), 1767-1780.

Osi, 2005. Hungarosaurus tormai, a new ankylosaur (Dinosauria) from the Upper Cretaceous of Hungary. Journal of Vertebrate Paleontology. 25(2), 370-383.

Osi and Mak
adi, 2009. New remains of Hungarosaurus tormai (Ankylosauria, Dinosauria) from the Upper Cretaceous of Hungary: Skeletal reconstruction and body mass estimation. Palaontologische Zeitschrift. 83, 227-245.

Parsons and Parsons, 2009. A new ankylosaur (Dinosauria: Ankylosauria) from the Lower Cretaceous
Cloverly Formation of central Montana. Canadian Journal of Earth Sciences. 46(10), 721-738.

Thompson, Parish, Maidment and Barrett, 2012. Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora). Journal of Systematic Palaeontology. 10, 301-312.

Kirkland, Alcal
a, Loewen, Esp
ılez, Mampel and Wiersma, 2013. The basal nodosaurid ankylosaur Europelta carbonensis n. gen., n. sp. from the Lower Cretaceous (Lower Albian) Escucha Formation of northeastern Spain. PLoS ONE. 8, e0080405.

Arbour, Zanno and Gates, 2016. Ankylosaurian dinosaur palaeoenvironmental associations were influenced by extirpation, sea-level fluctuation, and geodispersal. Palaeogeography, Palaeoclimatology, Palaeoecology. 449, 289-299.

Madzia, Arbour, Boyd, Farke, Cruzado-Caballero and Evans, 2021. The phylogenetic nomenclature of ornithischian dinosaurs. PeerJ. 9, e12362.

Raven, Barrett, Joyce and Maidment, 2023. The phylogenetic relationships and evolutionary history of the armoured dinosaurs (Ornithischia: Thyreophora). Journal of Systematic Palaeontology. 21(1), 2205433.

Russo and Mateus, 2023. Review of Dracopelta zbyszewskii, an ankylosaur from the Upper Jurassic of Portugal. 14th Symposium on Mesozoic Terrestrial Ecosystems and Biota. The Anatomical Record. 306(supp. 1), 221-223.

Are uncinate processes ancestral to Archosauria? A look at Wang et al 2023

A paper was published on January 17th (Wang et al., 2023) that I've been looking forward to since its SVP 2020 poster (Wang et al., 2020).  The basic idea is that uncinate processes leave attachment scars on ribs even if the processes themselves are unossified, and these scars show that uncinate processes were much more widespread than the record of ossified processes would suggest.  In theropods, ossified uncinate processes are only known in many pennaraptorans, Pelecanimimus and the noasaurid "Sidormimus" (Sereno, 2010; not mentioned by Wang et al., 2023) for instance, but Wang et al. found scars in Struthiomimus, Gorgosaurus and Allosaurus, all of which definitely lacked ossified processes.  Similarly, Wang et al. identified scars in Apatosaurus, when I don't think any sauropodomorph has been reported with ossified processes.

So my first question in 2020 was "do any archosaurs NOT show these scars?", and the SVP abstract and poster didn't say.  Even in the published paper, the most we get in the main section is "Using an alternate coding approach in which uncinate processes were coded as absent in taxa represented by five or more dorsal vertebral ribs that all lacked uncinate scars, nine archosaur taxa were coded as lacking uncinate processes."  Which nine taxa?  Who knows.  The Methods section at the end of the paper similarly says "Our alternative coding approach, which was used to test the stability of the results obtained under our preferred coding approach, differed in that uncinate processes were coded as absent in taxa for which at least five vertebral ribs were available, regardless of their state of preservation, and showed no sign of uncinate processes or uncinate scars. This resulted in coding uncinate processes as absent in nine taxa."  It does detail that their outgroup, the proterochampsian Chaneresuchus, lacks the scars so was assumed to lack any uncinate processes, but that's it.

Their only figure besides two showing the scars is Figure 3, an "informal consensus cladogram", whose caption reads "Major clades of Archosauria with evidence of cartilaginous uncinate processes are labelled and shaded blue; clades with evidence of ossified uncinate processes are labelled and shaded pinkish red; clade with evidence of both cartilaginous and ossified uncinate processes is labelled and shaded purple; and clades for which no evidence is available are labelled and shaded grey."  Clades shaded gray are Shartegosuchidae, Pachycephalosauria, Macronaria and Megalosauroidea, the latter being the most basal theropod clade shown.  I guess the nine mystery taxa belong to those clades?  Also note every branch in each blue clade is blue, every branch in every red clade is red, etc., implying homogeniety.  Here's the figure-

 

It turns out the identity of the Mystery Nine is in Table 2 of the Supplementary Information, under Alternate Coding.  In the preceding paragraph they again report "Under the alternate coding method, nine taxa were scored as lacking uncinate processes."  These taxa are- Lotosaurus, Protosuchus, Lagerpeton, Plateosaurus, Anchisaurus, Camarasaurus, Camptosaurus, Parasaurolophus, Edmontosaurus, Protoceratops and Chasmosaurus.  Wait, that's actually eleven taxa, not nine, despite the number nine being stated three times.  On the one hand, note none of these are shartegosuchids, pachycephalosaurs, or megalosauroids, so why are those clades even in the cladogram?!  On the other hand, note that Lotosaurus and Protosuchus would make two gray nodes basal to mesoeucrocodylians, Lagerpeton would be a gray node basal to dinosaurs, and Plateosaurus and Anchisaurus would be two extra gray nodes basal to sauropods.  Also all of the Ornithopoda and Ceratopsida [sic] branches are blue when they shouldn't be.  So the figure is putting in artificial discrepancy and leaving out most of the actual discrepancy.

The big methodological problem with the paper is that their Preferred Coding approach scored "the presence of uncinate processes as uncertain (?) if evidence of uncinate processes or scars was lacking."  So the Mystery "Nine" were actually all scored as unknown, even though Chaneresuchus was scored as absent (0) based on identical evidence.  So obviously if you score all the archosaurs as present or unknown and the sole non-archosaur as absent, you're going to get archosaurs ancestrally having uncinate processes.  And when they use the Alternate Coding of taxa without scars not having uncinate processes, they themselves report-

"Maximum likelihood and Bayesian inference recovered cartilaginous uncinate processes as the most likely condition at Archosauria (pml=0.61, pmb=0.55), but only when branch length estimates were incorporated. By contrast, maximum likelihood excluding branch length estimates recovered the absence of uncinate process as the most likely condition at Archosauria (pml=0.92). The ancestral condition at Dinosauria could not be recovered with confidence using either maximum likelihood or Bayesian inference (pml=0.57, pmb ≈ 0.33). Maximum likelihood recovered ossified uncinate processes as the most likely condition at Maniraptoriformes (pml=0.90) and Pennaraptora (pml=0.99), but only when branch length estimates were excluded from the analysis. Bayesian inference could not confidently recover the ancestral conditions at Maniraptoriformes (pmb=0.33) and Pennaraptora (pmb=0.33)."

So not strongly supporting "deep reptilian evolutionary roots of a major avian respiratory adaptation", and that's not even going into how the only non-avian paravians they scored were four dromaeosaurids (Microraptor, Saurornitholestes, Velociraptor and Deinonychus) with ossified processes, when at least Archaeopteryx, anchiornithines and omnivoropteryids lacked them, so anything about Pennaraptora's ancestral state is going to need more than "oviraptorosaurs, dromaeosaurids, Rhea, Gallus and Lithornis - yes, Chauna - no."

And yeah, the living bird Chauna has no uncinate processes and lacks any scars for them, so was rightfully scored 0.  Yet fossil taxa with the same morphology were scored unknown.  Which again points to the flaw in their Preferred Coding, but also suggests we might expect homoplasy in other parts of Archosauria as well.  So lambeosaurines and edmontosaurins could have lacked uncinates while kritosaurins had them, following the osteological evidence, for instance.

In conclusion, it's an excellent idea to look for osteological correlates to unossified uncinate processes, and we got some real data hidden in the supplementary information, but any use was marred by unforced errors like a misleading main figure and a nonsensical scoring methodology.  I wouldn't doubt uncinates were primitive to at least averostrans, given "Sidormimus" and Edmarka (check Figure 14A of Bakker et al., 1992; so Megalosauroidea should have ironically been blue), but the concept deserved better vetting than this.

References- Bakker, Kralis, Siegwarth and Filla, 1992. Edmarka rex, a new, gigantic theropod dinosaur from the Middle Morrison Formation, Late Jurassic of the Como Bluff outcrop, with comments on the evolution of the chest region and shoulder in theropods and birds and a discussion of the five cycles of originn and extinction among giant dinosaurian predators. Hunteria. 2(9), 1-24.

Sereno, 2010. Noasaurid (Theropoda: Abelisauroidea) skeleton from Africa shows derived skeletal proportions and function. Journal of Vertebrate Paleontology. Program and Abstracts 2010, 162A.

Wang, Sullivan and LeBlanc, 2020. Anatomical and histological data indicate uncinate processes to be homologous across Archosauria. Journal of Vertebrate Paleontology. Program and Abstracts 2020, 334.

Wang, Claessens and Sullivan. 2023. Deep reptilian evolutionary roots of a major avian respiratory adaptation. Communications Biology. 6:3.

"Scrotum humanum" a torvosaur and Jurassic Chinese theropod updates - The Theropod Database January 2023

Happy New Years everyone!  Sorry about how long it took to post the update, but I was covering too many sections at once.

Darren Naish's post on Middle Jurassic British theropod femur OUMNH J29757 and "Scrotum humanum" led me to do something that's been on my list for a while- compare the one original figure of "Scrotum" to other theropods to see if is really Megalosaurus as has long been assumed.  Turns out it's closer to another closely related taxon...


"Scrotum" Brookes, 1763
"S. humanum" Brookes, 1763
Aalenian-Bajocian?, Middle Jurassic
unknown quarry, Inferior Oolite?, Cornwell, England
Material- (lost) distal femur (~235 mm trans)
Diagnosis- (proposed) ectocondylar tuber limited to medial half of ectocondyle; ectocondyle subequal in size and shape to endocondyle.
Comments- Originally described and illustrated by Plot (1677) as the distal femur of a giant human, this is famous as being the first Mesozoic dinosaur bone to be published. Brookes (1793) later summarized Plot's description and opinions but labeled the specimen Sctrotum Humanum in his plate. Rieppel (2022) notes that "At the top of page 317, Brookes (1763) noted that 'other stones have been found exactly representing the private parts of a man; and others in the shape of kidneys . . . ', and continued further down on the same page" described the femur.  As "the plates and the individual figures they contain are not numbered separately, but are identified by the pagination number of the page on which the respective specimens are mentioned or described. The conclusion seems to be that the illustrator took the femur fragment to be an example of those stones referred to on page 317 as 'exactly representing the private parts of a man', and erroneously labelled it accordingly."  Phillips (1871) believed it was from the Inferior Oolite (Aalenian-Bajocian) and stated "It may have been the femur of a large megalosaurus or a small ceteosaurus" without evidence.  As described by Delair and Sargeant (1975), Halstead (1970) "pointed out that because of its date of publication (post-Linnean, i.e. after 1758), this binomen can be considered a perfectly valid publication of the first generic and specific name ever applied to dinosaurian remains. It is perhaps fortunate that the name was not thereafter employed by any subsequent worker, and thus Scrotum humanum Brookes must be treated as a nomen oblitum and discarded."  They (and Halstead) considered it more probable to be Megalosaurus than Cetiosaurus without evidence and stated "The specimen unfortunately is lost."  Halstead and Sarjeant (1993; publication duplicated in 1995) noted that while Scrotum should be treated as a nomen oblitum under ICZN Article 23b (First Edition), "no application was made then, or has been made since, for the formal suppression of Brookes's binomen."  The Third Edition of the ICZN came out in 1985 and eliminated the nomen oblitum clause, so the authors petitioned the ICZN in 1992 "(I) to use its plenary powers to suppress the generic name Scrotum Brookes, 1763 and the specific name S. humanum Brookes, 1763; (2) to retain on the Official List of Generic Names in Zoology the name Megalosaurus Buckland in Parkinson, 1822, type species by subsequent designation M. bucklandi Meyer. 1832. (3) to retain on the Official List of Specific Names in Biology the name bucklandi as published in the binomen Megalosaurus bucklandi (specific name of the type species of Megalosaurus Buckland in Parkinson, 1822, by designation in Meyer, 1832); (4) To place on the Official List of Rejected and Invalid Generic Names in Zoology the name Scrotum Brookes, 1763; (5) to place on the Official List of Rejected and Invalid Specific Names in Zoology the name humanum Brookes, 1763, as published in the binomen Scrotum humanum, and as suppressed in (1) above." as listed in 1993.  As recalled by the authors, Tubbs (Executive Secretary to the ICZN) replied later that year that "The text on p. 301 of Brookes (1763) makes it quite clear that the two words "Scrotum humanum" on the plate were a description of a specimen, and that Brookes did not establish a genus Scrotum or a species humanum (any more than he did a species Kidney stone on the same plate!). The words just happened to be Latin."  Furthermore, since "[the name Scrotum humanum] has never been used as a scientific name", it "is therefore unavailable under Article 11d of the Code" (Third Edition- "Names to be treated as valid when proposed. - Except as in (i) below, a name must be treated as valid for a taxon when proposed unless it was first published as a junior synonym and subsequently made available under the provisions of Section e of this article.").  Finally, because "Plot's long-lost specimen was ... not certainly, a Megalosaurus bone", Tubbs wrote that "the Commission is willing to take action only when there is an appreciable and real, as opposed to hypothetical, threat to stability or nomenclature. This is not the case for Megalosaurus."  Note that Tubbs was incorrect that Brookes ever specified Scrotum Humanum was a description instead of a name, with page 301 being an unrelated section on plant fossils, so his use of Article 11d was unwarranted although recently supported by Rieppel's logic.  He was also wrong that it had never been used as a scientific name, as Molnar et al. (1990) listed Scrotum humanum as a carnosaur nomen dubium.  Under the current ICZN, "Scrotum humanum" would be a nomen nudum based on Article 11.5- "To be available, a name must be used as valid for a taxon when proposed."  Tubbs was right that the referral to Megalosaurus was merely hypothetical though, as it has never been supported by published evidence and seems unwarranted.
The femur is dissimilar from Cetiosaurus (both the lectotype OUMNH J13615 and the Rutland specimen LCM G468.1968) in being 45-86% larger, having a distally extended medial condyle, and a fibular groove placed at the lateral edge.  Note the estimated transverse diameter is based on Plot's statement the narrowest shaft circumference was 15 inches (= 381 mm) and scaled from the figure.  Compared to this, Megalosaurus femora are slightly smaller (shaft diameter 265-343 mm), and differ in having a more distomedially extended and pointed medial condyle, more laterally positioned ectocondylar tuber, and a straight lateral edge until the distal extent of the tuber.  These same differences are also usually present in e.g. Cruxicheiros, piatnitzkysaurids, Eustreptospondylus, Erectopus, Allosaurus, and Juratyrant among large Jurassic theropods whose distal femora are undistorted and figured in posterior view.  If "Scrotum" is from the Inferior Oolite it is also earlier than Megalosaurus, and differs from the contemporaneous Magnosaurus in the same ways when preserved (more laterally positioned ectocondylar tuber; straight lateral edge until the distal extent of the tuber), although it could derive from Duriavenator with which it cannot be compared.  Sinraptor dongi is slightly more similar to "Scrotum" in having a convex lateral edge alongside the ectocondylar tuber, but it is "Brontoraptor" which is most similar in having that character, an evenly rounded medial condyle and a more medially placed ectocondylar tuber.  Torvosaurus (ML 632) shows the last character at least but cannot be evaluated for the rest, so "Scrotum" might be best characterized as a torvosaur and may relate to "Megalosaurus" "phillipsi" from the Kimmeridgian of England that also has characters similar to "Brontoraptor" and Torvosaurus.  "Brontoraptor" also has a similar circumference (376 mm) and internal cavity size based on Siegwarth et al.'s Figure 8E.  Whether the remaining differences (ectocondylar tuber limited to medial half of ectocondyle; ectocondyle subequal in size and shape to endocondyle) are genuine or illustration error caused by Plot generalizing then unfamiliar megalosauroid anatomy is uncertain.  Note "Scrotum" can be excluded from Ceratosauria based on the absence of a tall anteromedial crest, and from Coeluridae, Proceratosauridae and Maniraptoromorpha based on the deep extensor groove described by Plot and large size (with occasional exceptions, e.g. Yutyrannus).
References- Plot, 1677. The Natural History of Oxford-shire, being an essay towards the Natural History of England. Oxford. 358 pp.
Brookes, 1763. The Natural History of Waters, Earths, Stones, Fossils and Minerals, with their Virtues, Properties and Medicinal Uses: To which is added, the methods in which Linnaeus has treated these subjects. Vol. 5. J. Newberry. 364 pp.
Robinet, 1768. Vue philosophique de la gradation naturelle des formes de l'être, ou les essais de la nature qui apprend a faire l'homme. Harrevelt. 260 pp.
Phillips, 1871. Geology of Oxford and the Valley of the Thames. Oxford at the Clarendon Press. 523 pp.
Halstead, 1970. Scrotum humanum Brookes 1763 - the first named dinosaur. Journal of Insignificant Research. 5(7), 14-15.
Delair and Sargeant, 1975. The earliest discoveries of dinosaurs. Isis. 66, 5-25.
Buffetaut, 1979. A propos du reste de dinosaurien le plus anciennement décrit: l'interprétation de J.-B. Robinet (1768). Histoire et Nature. 14, 79-84.
Molnar, Kurzanov and Dong, 1990. Carnosauria. In Weishampel, Dodson and Osmolska (eds.). The Dinosauria. University of California Press. 169-209.
Halstead and Sarjeant, 1993. Scrotum humanum Brookes - the earliest name for a dinosaur? Modern Geology. 18, 221-224.
Halstead and Sarjeant, 1995. Scrotum humanum Brookes - the earliest name for a dinosaur? In Sarjeant (ed.), 1995. Vertebrate Fossils and the Evolution of Scientific Concepts; A tribute to L. Beverly Halstead. Gordon and Breach. 219-222.
Delair and Sargeant, 2002. The earliest discoveries of dinosaurs: The records re-examined. Proceedings of the Geologists' Association. 113, 185-197.
Rieppel, 2022 (online 2021). The first ever described dinosaur bone fragment in Robinet's philosophy of nature (1768). Historical Biology. 34(5), 940-946.

"Scrotum humanum" distal femur (lost; leftmost; after Plot, 1677), compared to (left to right) "Brontoraptor" (TATE 0012; after Siegwarth et al., unpublished), Megalosaurus bucklandii (NHMUK 31806; after Benson, 2010b), Magnosaurus nethercombensis (OUMNH J12143; after Benson, 2010a).

Also updated is Chienkosaurus, which thanks to the recent description of Sinraptor dongi teeth by Hendrickx et al. (2020), I feel can be placed in Metriacanthosauridae.  This and Szechuanosaurus were coincidentally recently reviewed by Curtice at his blog I've started following, Dr. BC's Hindsight at Fossil Crates, which I highly recommend.

Chienkosaurus Young, 1942
C. ceratosauroides Young, 1942
Tithonian?, Late Jurassic
IVPP locality 47, upper Guangyuan Group, Sichuan, China
Lectotype- (IVPP V237A) (~8 m) posterior premaxillary tooth (44x16x12 mm)
Referred- ?(IVPP V193) ulna (164 mm) (Young, 1942)
Bathonian-Callovian?, Middle Jurassic
IVPP locality 49, middle Guangyuan Group, Sichuan, China
?(IVPP V190) (~5 m) ~ninth caudal centrum (66 mm) (Young, 1942)
Other diagnoses- Young (1942) originally diagnosed Chienkosaurus with- "Teeth thick and sharply pointed with fine palisade denticulations on both sides. The anterior which are finer than the posterior ones push lingually
towards the base and form a ridge topping at a distance before the base of the tooth."
Comments- The material was discovered in late Spring 1941, with the type consisting of four isolated teeth IVPP V237A-D.  Young's (1942) diagnosis was "Mainly based upon" the largest tooth (V237A), with the three smaller teeth considered immature and (possibly incorrectly) lacking their bases.  He stated "The general shape of the teeth resembles that of Labrosaurus stechowi" which was prescient as both are based on mesial dentition, and considered Chienkosaurus a ceratosaurid based on the questionably referred postcrania.  Ironically, "Labrosaurus" stechowi is now thought to be ceratosaurid, but as Young noted Chienkosaurus lacks its lingual fluting which has proven to be a ceratosaurid character.  Subsequently, Chienkosaurus was generally placed in Megalosauridae (e.g. Romer, 1956; Steel, 1970; Dong et al., 1978) when it was used as a waste basket for almost all large Jurassic theropods including Ceratosaurus and later Yangchuanosaurus.  Note Huene (1959) when citing Chienkosaurus as named in 1958 from the Late Cretaceous of Shantung meant to list Chingkankousaurus.  Dong et al. (1983) reported that "Rozhdestvensky (1964) proposed that the four teeth of Chienkosaurus could possibly belong to the Crocodilia" (translated), but which work this corresponds to was not listed in the bibliography and cannot be determined.  Dong et al. also stated "during the editing of "The Handbook of Chinese Fossil Vertebrates," Zhiming Dong conducted a review of these four specimens and formally confirmed that the best preserved tooth among the V237 collection was a premaxillary tooth of a carnosaurian dinosaur, but that the remaining three teeth were assignable to the crocodile Hsisosuchus."  The dentition of Hsisosuchus has not been described or figured in enough detail to distinguish it from theropods, but two of the teeth (IVPP V237B and V237D) are similar in being short and barely recurved with a high crown base ratio, characters shared with the tooth figured separately in Hsisosuchus' type description.  They are provisionally placed in Hsisosuchus sp. here.  The third supposed Hsisosuchus tooth (IVPP V237C) is different in having a distinctly D-shaped section with strong carinae somewhat like Guimarota tyrannosauroid premaxillary tooth IPFUB GUI D 89, so is provisionally placed in Tyrannosauroidea here.  Retaining only one of Chienkosaurus' syntype teeth in the genus would make it the lectotype, and as ICZN Article 74.5 states "In a lectotype designation made before 2000, either the term "lectotype", or an exact translation or equivalent expression (e.g. "the type"), must have been used or the author must have unambiguously selected a particular syntype to act as the unique name-bearing type of the taxon", and Dong et al. explicitly make Chienkosaurus a synonym of Szechuanosaurus, and of Chienkosaurus' syntypes only consider IVPP V237A to be theropodan, this is here considered a valid lectotype designation.  Rozhdestveksy (1977) earlier listed Szechuanosaurus campi and Chienkosaurus ceratosauroides as "synonyms?" in his Table 1 without comment, while Dong et al.'s synonymization was based on examining Yangchuanosaurus teeth from CV 00214 to correctly determine "the differences among carnosaur dentitions are due only to being in a different position in the dentition" and noting Chienkosaurus' and Szechuanosaurus' types are from the same locality.  While this indeed makes it possible they even derive from the same individual, none of the teeth have been shown to be diagnostic within metriacanthosaurids, and synonymization should be based on autapomorphies or unique combinations of characters instead of provenance.  This synonymization of part of the Chienkosaurus type with Szechuanosaurus was followed by Molnar et al. (1990) where they consider the taxon an allosaurid, which makes sense as Dong was a coauthor.  Most recently, Hendrickx et al. included Chienkosaurus in their cluster analyses, although the taxon is never mentioned in the text, matrices or table of examined taxa.  Classical/Hierarchical clustering resolves it with Genyodectes, Sinraptor dongi (the only metriacanthosaurid analyzed there) and Allosaurus, while neighbour joining clustering resolves it sister to a clade whose basal members are 'Indosuchus' AMNH jaws, Allosaurus and S. dongi. 
Young placed locality 47 at "the top part of the Kuangyuan Series and immediately below the Chentsianyen conglomerate", now known as the Guangyuan Group and the Chengqiangyan Group, with the former corresponding to the Xiashaximiao Formation through the Penglaizhen Formation.  As it was found "immediately below" the boundary (layer 8b in Young et al., 1943), Chienkosaurus may be from the Penglaizhen Formation or slightly lower Shuining Formation.  The age is listed as Tithonian on fossilworks and in Weishampel (1990), the latter cited as from "Dong (pers. comm.)". 
The tooth is similar to many large theropod teeth in general characters, but is from the premaxilla as evidenced by the twisted mesial carina and reduced extent of mesial serrations. The crown base ratio (.75) is between the third and fourth premaxillary teeth of Sinraptor dongi's holotype (pm3 .60; pm4 1.04), which also match in size (pm3 FABL 16.87 mm; pm4 BW 12.26 mm) and in lacking mesial serrations basally.  The cited mesial (15 per 5 mm) and distal (6.7-10 per 5 mm) serration densities are matched by teeth of S. dongi, and the strong mesial carina Young describes could easily be due to the "longitudinal groove adjacent to the mesial carina, on the lingual surface of the crown" "clearly present in lpm3 and lpm4" as described by Hendrickx et al. (2020) for S. dongi.  Thus Chienkosaurus is indistinguishable from Sinraptor dongi as far as can be determined from the description, and given its poorly constrained age could be contemporaneous or even synonymous.  Hendrickx et al.'s matrices show no differences between Yangchuanosaurus shangyouensis (including Y. magnus), Sinraptor dongi and S. hepingensis that can be evaluated for Chienkosaurus, so pending Hendrickx's in prep. study on metriacanthosaurid dental anatomy the genus is considered Metriacanthosauridae indet..
Referred material- Young (1942) figured and described an ulna from the type locality (IVPP V193), stating he "would prefer to refer this ulna to Chienkosaurus ceratosauroides above described."  The element is very different from Limusaurus in having marked transverse expansions proximally and distally as well as a triangular versus reniform proximal end, so that if Sinocoelurus is closely related to that genus the ulna is unlikely to belong to it.  Eoabelisaurus has a much longer olecranon.  The ulnae of megalosaurids and Kaijiangosaurus is far more robust with more proximally extended olecranons, while those of most coelurosaurs (e.g. Zuolong, Guanlong, Coelurus, Tanycolagreus, Fukuivenator) are much more slender with developed olecranons as well.  Fukuiraptor has a dissimilar ulna with a strong olecranon, prominent anteroproximal longitudinal ridge and unexpanded distal end.  This leaves several roughly comparable taxa whose ulnae have been figured in anteroposterior view- Ceratosaurus, Poekilopleuron, Yangchuanosaurus, Allosaurus and Haplocheirus.  Young compared it favorably to the former, writing "it fits rather well with the ulna of Ceratosaurus nasicornis (length of ulna, 17.7 cm.) which is only slightly longer than the present form", and indeed the main difference in profile is the more gradual proximal expansion laterally.  However, in proximal view IVPP V193 differs from Ceratosaurus and most other proximally figured ulnae in having a centrally placed olecranon (also seen in Coelurus, but not Tanycolagreus).  While only photographed in anterior view, the ulna of Yangchuanosaurus (CV 00214) would also seem to have a centrally placed olecranon, so IVPP V193 may be correctly referred to Chienkosaurus/Szechuanosaurus after all.
Young (1942) describes IVPP V190 as "A complete centrum of an anterior caudal vertebra (or posterior lumbar) with length 66 mm., breadth 41 mm., minimum breadth of the centrum 24 mm", noting it "fit in size with Chienkosaurus ceratosauroides" and calling it Theropoda indet. in the plate caption but also saying there it "probably belonging to Chienkosaurus ceratosauroides."  With a length/height ratio of 144% it is comparable to the ninth caudal of Sinraptor hepingensis and indistinguishable in lateral view.  It differs in being 85% wider than tall vs. 95%, but this is within the range of variation in hepingensis' caudals.  Notably, this is from a different locality than the type, said by Young to be in "the middle part of the" ... "Kuangyuan Series", layer 5a in Young et al. (1943), and thus possibly corresponding to the Shangshaximiao Formation.  Thus while lacking a plausible connection to Chienkosaurus, it is congruent with being metriacanthosaurid but may also be e.g. piatnitzkysaurid or megalosaurid.
References- Young, 1942. Fossil vertebrates from Kuangyuan, N. Szechuan, China. Bulletin of the Geological Society of China. 22(3-4), 293-309.
Young, Bien and Mi, 1943. Some geologic problems of the Tsinling. Bulletin of the Geological Society of China. 23(1-2), 15-34.
Romer, 1956. Osteology of the Reptiles. University of Chicago Press. 1-772.
Huene, 1959. Saurians in China and their relations. Vertebrata PalAsiatica. 3(3), 119-123.
Steel, 1970. Part 14. Saurischia. Encyclopedia of Paleoherpetology. Gustav Fischer Verlag. 1-87.
Rozhdestvensky, 1977. The study of dinosaurs in Asia. Journal of the Palaeontological Society of India. 20, 102-119.
Dong, Zhang, Li and Zhou, 1978. [A new carnosaur discovered in Yongchuan, Sichuan]. Chinese Science Bulletin. 23(5), 302-304.
Dong, Zhou and Zhang, 1983. Dinosaurs from the Jurassic of Sichuan. Palaeontologica Sinica. Whole Number 162, New Series C, 23, 136 pp.
Molnar, Kurzanov and Dong, 1990. Carnosauria. In Weishampel, Dodson and Osmolska (eds.). The Dinosauria. University of California Press. 169-209.
Weishampel, 1990. Dinosaurian distribution. In Weishampel, Dodson and Osmolska (eds.). The Dinosauria. University of California Press. 63-139.
Hendrickx, Stiegler, Currie, Han, Xu, Choiniere and Wu, 2020. Dental anatomy of the apex predator Sinraptor dongi (Theropoda: Allosauroidea) from the Late Jurassic of China. Canadian Journal of Earth Sciences. 57(9), 1127-1147.

Lectotype tooth of Chienkosaurus ceratosauroides in mesial and basal views (after Young, 1942).

Also newly revealed to be metriacanthosaurid is "Yuanmouraptor"-

"Yuanmouraptor" Anonymous, 2014
Middle Jurassic
Yuanmou County, Yunnan, China
Material- (ZLJ 0115) partial skull, mandibles (one incomplete, one partial), postcrania
Comments- This specimen is on display at the ZLJ as a new carnosaur, but has yet to be described. There is a mounted skeleton, but how much is original is unreported.  Hendrickx et al. (2019) call this "an undescribed metriacanthosaurid (ZLJT 0115)", state it has mesial and lateral teeth with "four to six, possibly more" flutes, and list it as "Metriacanthosauridae indet." in their Appendix 1 indicating information was from photos provided by Stiegler.
References- Anonymous, 2014. Special Exhibition: Legends of the Giant Dinosaurs. Hong Kong Science Museum newsletter. 1-3-2014, 2-7.
Hendrickx, Mateus, Araújo and Choiniere, 2019. The distribution of dental features in non-avian theropod dinosaurs: Taxonomic potential, degree of homoplasy, and major evolutionary trends. Palaeontologia Electronica. 22.3.74, 1-110.


As part of a review of Jurassic Chinese theropods, I went over the largest Jurassic theropod, previously referred to Szechuanosaurus campi.

unnamed averostran (Camp, 1935)
Middle Jurassic?
Jung-Hsein UCMP V1501, middle Chongqing Group, Sichuan, China
Material- (UCMP 32102) (~14.7 m) mesial dentary tooth (~69x~22x? mm), rib fragment, ischial fragment, femoral fragment (~1.33 m)
Comments- The specimen was collected on August 30 1915 by Louderback.  Note the UCMP locality number is V1501 (as determined in their online catalogue), not V151 as listed by Camp.  Jung-Hsien is now called Rongxian, a county in Zigong City.  Camp stated "The beds in which they occur have been called the Szechuan series", which was a term for the stratigraphic section from the Early Jurassic Qianfuyan (= Tsienfuyan) Formation and Ziliujing (= Tsuliuching, = Tzeliutsin) Formation to the Cretaceous Chengqiangyan (= Chengtsiangyen) Group and Jiading (= Chiating, = Tshiating) Group, depending on north versus south in the Sichuan Basin. Rongxian is located in the south, so UCMP V1501 would be part of the Ziliujing-Chongqing-Jiading sequence, and Young (1937; see also Young et al., 1943) placed it above the Ziliujing Formation but below the conglomerates of the Jiading Group, and thus within the Middle-Late Jurassic Chongqing Group.  Furthermore, Young (1937) stated "The fossiliferous horizon discovered by Louderback lies probably between our horizons 2 and 3, some 200 meters above horizon 2" which is the type locality of Omeisaurus junghsiensis.  As Omeisaurus is generally recovered in the Xiashaximiao Formation and horizon 3 is another 300 meters above where Young placed UCMP V1501 (so may be the Penglaizhen or Suining Formation), UCMP 32102 may derive from the Shangshaximiao Formation.  Dong et al. (1983) listed it as deriving from that formation, perhaps using the same logic although they did not describe any explanation.
Camp (1935) initially referred the specimen to Megalosauridae because histology "shows quite definitely that the relationship of the Chinese form is with Allosaurus" instead of Tyrannosaurus.  However, the plate shows this is because the sampled section of Tyrannosaurus femur (labeled AMNH 5886, but this is the Anatotitan paratype, and it is more probably Dynamosaurus holotype AMNH 5866 that is known to be histologically sampled) is composed of secondary osteons, while those of Allosaurus and UCMP 32102 are fibrolamellar bone.  Yet Allosaurus can develop secondary osteons where bone is redeveloped as well (e.g. MHNG GEPI V2567a), so this isn't a real difference between these taxa.  While Camp wrote "a projection of the borders would indicate an original total length of at least 90 mm" for the tooth, he also repeated Osborn's 1906 statement that Tyrannosaurus (CM 9380 and NHMUK R7994) teeth are up to 125 mm, which includes the root.  Combined with his statement the serrated distal carina "reaches the base of the enamel" and serrations are not illustrated on the most basal section, the actual crown length would have been about 69 mm.  Similarly, Camp wrote "At the base it is 17 mm. in longest diameter", but scaling the figured tooth to the stated preserved length of 60 mm results in a FABL of 22 mm instead.  Young (1942) later wrote "The general structure of [Szechuanosaurus campi syntype] V236 with the way of serrations fits so well with the Junghsien tooth, we feel that there is practically no doubt in regarding them as identical" "and prefer to consider the Junghsien tooth as belonging also to the new form" Szechuanosaurus.  This despite previously stating UCMP 32102 "is bigger and straighter than all" Szechuanosaurus syntype teeth.  Compared to Sinraptor dongi and Szechuanosaurus, UCMP 32102 is larger (~69 vs. up to 63 vs. ~32 and ~47 mm), with a much greater crown height/base ratio (~314% vs. up to 244% vs. ~224% and ~267%), making it less tapered.  The crown section is similar to Allosaurus' fourth dentary tooth and the mid crown ratio of 53% is similar to dentary teeth in S. dongi and between S. campi IVPP V238B and 238C.  As in mesial teeth of S. dongi, the crown is slightly lingually curved and the mesial carina does not reach the crown base.  The same serration densities (mesial 15 per 5 mm, distal 6.7-10 per 5 mm) can be found in S. dongi as well, but are lower than S. campi (distal ~12-19 per 5 mm).  Dong et al. (1983) wrote "Camp's description and the dentition size suggests it may be assignable to Yangchuanosaurus", but it is larger than even the magnus type (up to 75 mm), and more elongate than the largest maxillary teeth of the genotype (crown height/base ratio of 267%), but detailed dental statistics of the genus have yet to be published.  The femoral fragment is notably large, Camp stating the shaft has "an enormous hollow cavity about 125 mm. in the longest diameter of its ellipse. The greatest diameter of this segment at its narrowest point is 20 cm."  Based on the absence of a fourth trochanter or medial narrowing, the section is just distal to the former structure.  Here large theropod femoral shafts are wider than deep, so 200 mm would be the width and the figured depth is then ~143 mm.  Scaling from the largest metriacanthosaurid, Yangchuanosaurus magnus, results in a femoral length of ~1.33 meters, not far from Camp's "estimated total length of about 140 cm."  The ischium "consists of a moderately hollow shaft spreading into a broader, solid plate", which could describe most non-maniraptoran ischia, while the "tip of a large rib" is not described.  Notably, the ischium was found 37 meters from the other material, so its association is less certain.
Given the above information, UCMP 32102 is different from the Szechuanosaurus syntypes and anteriorly straighter than Sinraptor as well, and is perhaps the largest known Jurassic theropod.  As no characters are outside the range of ceratosaurids, it is considered Averostra incertae sedis here.
References- Camp, 1935. Dinosaur remains from the province of Szechuan. University of California Publications, Bulletin of the Department of Geological Sciences. 23(14), 467-471.
Louderback, 1935. The stratigraphic relations of the Jung Hsien fossil dinosaur in Szechuan red beds of China. University of California Publications. Bulletin of the Department of Geological Sciences. 23(14), 459-466.
Young, 1937. New Triassic and Cretaceous reptiles in China (With some remarks concerning the Cenozoic of China). Bulletin of the Geological Society of China. 17(1), 109-120.
Young, 1942. Fossil vertebrates from Kuangyuan, N. Szechuan, China. Bulletin of the Geological Society of China. 22(3-4), 293-309.
Young, Bien and Mi, 1943. Some geologic problems of the Tsinling. Bulletin of the Geological Society of China. 23(1-2), 15-34.
Dong, Zhou and Zhang, 1983. Dinosaurs from the Jurassic of Sichuan. Palaeontologica Sinica. Whole Number 162, New Series C, 23, 136 pp.

UCMP 32102 tooth (top) and femoral shaft (bottom) (after Camp, 1935).

Finally, I've been translating He (1984), so here's that publication's supposed Szechuanosaurus-

unnamed Tetanurae (He, 1984)
Bathonian-Callovian, Middle Jurassic
Hexi Commune, Shangshaximiao Formation, Sichuan, China
Material- (CUT coll; = CCG coll) (multiple individuals) many teeth (~63 mm), anterior cervical centrum (~68 mm; immature; Fig. 6-16, Pl. X Fig. 3), mid cervical vertebra (~69 mm; Fig. 6-17), tenth cervical centrum (immature; Fig. 6-19a), ~second dorsal centrum (~55 mm; immature?; Pl. X Fig. 4), incomplete ~fourth dorsal vertebra (Fig. 6-19b), mid dorsal centrum (immature; Fig. 6-19c), more than forty caudal vertebrae including proximal caudal vertebra (Fig. 6-19d) and distal caudal vertebra (~70 mm; Pl. X Fig. 5), incomplete coracoid (~98 mm proximodistally), humerus (265 mm), ischium (~356 mm), femur, tibia (~730 mm), fibula (~709 mm) and unguals
Comments- He (1984) states that in 1964, 1979 and 1980 in Chengdu the institute (= CUT) "conducted systematic collections in Hexi Commune (near Huomu Station) in the suburbs of Qingyuan City, including many carnosaur specimens, including many teeth, cervical vertebrae, dorsal vertebrae, more than forty caudal vertebrae, complete ischium, femur, tibia and fibula, as well as relatively complete humerus, coracoid and claws." (translated)  He referred these to Szechuanosaurus campi because the syntypes were also found in the suburbs of Guangyuan and believed to be from the Shangshaximiao Formation based on faunal similarities and fossil abundance, "there is no significant difference in shape and size" between S. campi and the Hexi teeth, and "there is no evidence of the existence of two or more carnosaurs" from that horizon.  However, the teeth of S. campihave not been shown to be diagnostic within e.g. Metriacanthosauridae, multiple taxa with megalosaur-grade teeth are now known from the Shangshaximiao (Leshansaurus, Yangchuanosaurus shangyouensis, Sinraptor hepingensis), and S. campi itself may be from the Penglaizhen Formation or slightly lower Shuining Formation instead.  Furthermore, He notes "that the tooth size in this batch of Szechuanosaurus campi material we collected is quite varied, which means that in addition to the differences in individual size, there may also be immature specimens, because some vertebral centra and neural arches are unfused. The largest individual is comparable to the type of Yanchuanosaurus shangyouensis [sic], and the smallest individual is estimated to be only 4-5 meters in length."  Thus multiple individuals and perhaps multiple taxa are involved, with only the tibia and fibula in Plate X Figures 8-10 being claimed to be from one individual.  Note while Chure (2000) mentioned a metatarsal as being in this material, He does not indicate as such and Chure might have mistaken Plate X Figure 6 which is a humerus.  Indeed, Chure seems not to have translated the text so understates the preserved vertebral number and misses the reference to unguals.  Yang et al. (2021) later describe the humeral histology, noting their Szechuanosaurus specimen is from Hexi and citing He's paper.  This paper confirms the material "contains several incomplete individuals with large differences in size" (translated), that "The specimen is currently preserved in the Museum of Chengdu University of Technology" and that it was recovered from the Shangshaximiao Formation at the same locality as Mamenchisaurus "guangyuanensis".  "One of the medium-sized individuals was recovered, mounted and exhibited", which is photographed in their Figure 2, although it cannot be determined what material is real and what is plaster.
This material was originally referred to Megalosauridae by He (1984) based on tetanurine plesiomorphies (large teeth, short presacral vertebrae, distally expanded ischium), while Chure (2000) placed it in non-avetheropod Tetanurae based on the supposed lack of a posterodistal coracoid process and subglenoid fossa, although Figure 6-18 of He clearly shows both.  Although Chure believes the information available in the literature "make(s) it impossible to refer this material to any family" and considered it indeterminate, the figures and plates suggest otherwise.  Among Late Jurassic theropods, the slightly opisthocoelous cervicals are only known in piatnitzkysaurids and coelurosaurs, with the long and low neural spines being unlike most contemporary non-coelurosaur theropods, meaning the mid cervical vertebra at least is not megalosauroid or carnosaurian.  Similarly, the large coracoid tubercle is unlike basal tetanurines and more similar to ceratosaurs or coelurosaurs, although lacking the hypertrophied size of the former.  As suggested by Chure, the ischium does resemble Megalosaurus in the ventral kink of the shaft and boot morphology, although it is much more robust, thus a referral to Leshansaurus is plausible.  The tibia on the other hand is more similar to Sinraptor in the anteroposteriorly short proximal end and anteroposterior compression distally, so may be metriacanthosaurid.  Based on this brief comparison, the material deserves restudy and probably represents multiple tetanurine taxa.
References- He, 1984. The Vertebrate Fossils of Sichuan. Sichuan Scientific and Technical Publishing House, Chengdu, Sichuan. 168 pp.
Chure, 2000. A new species of Allosaurus from the Morrison Formation of Dinosaur National Monument (Utah-Colorado) and a revision of the theropod family Allosauridae. PhD thesis. Columbia University. 964 pp.
Yang, Liu and Zhang, 2021. The humeral diapophyseal histology and its biometric significance of Jurassic Szechuanosaurus campi (Theropoda, Megalosauridae) in Guangyuan City, Sichuan Province. Acta Geologica Sinica. 95(8), 2318-2332.

Tetanurae elements from He (1984)- 1, 2 teeth; 3 anterior cervical centrum; 4 ~second dorsal centrum; 5 distal caudal vertebra; 6 humerus; 7 ischium; 8 tibia in anterior and distal views; 9 fibula in lateral and distal views; 10 tibia and fibula in proximal view (after He, 1984).

Additional references- Siegwarth, Lindbeck, Redman, Southwell, unpublished. Giant carnivorous dinosaurs of the family Megalosauridae from the Late Jurassic Morrison Formation of eastern Wyoming. Contributions from the Tate Museum Collections, Casper, Wyoming. 2, 40 pp.

Benson, 2010b. The osteology of Magnosaurus nethercombensis (Dinosauria, Theropoda) from the Bajocian (Middle Jurassic) of the United Kingdom and a re-examination of the oldest records of tetanurans. Journal of Systematic Palaeontology. 8(1), 131-146.

Benson, 2010b (online 2009). A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods. Zoological Journal of the Linnean Society. 158(4), 882-935.

The Theropod Database July update - Iren Dabasu theropods

As mentioned by Justin Tweet last month, we haven't had that many new dinosaur taxa described lately, whether due to COVID or random chance.  But this doesn't bother me because there is always so much data to catch up on.  In mid May I checked my Database suggestion emails and the most recent topic to address was "Brochu (2003) mentions that the specimen AMNH 6266 (including a jugal, lacrimal, quadratojugal, and D-shaped premaxillary tooth) might belong to the holotype of Alectrosaurus olseni as it was found at the type locality of A. olseni."  And because of that, we now have all published Iren Dabasu theropod records added and updated on The Theropod Database.  I'll go over some of the lesser known and new details about select taxa here.  There was nothing particularly new about Erliansaurus, Neimongosaurus or Gigantoraptor, so I don't list them below.  If anyone knows of any Iren Dabasu theropod specimens in the literature I missed, do leave a comment.  One thing that struck me was just how much material remains undescribed, at the AMNH, IVPP and PIN especially.  If anyone needs projects based on collected material- sort out Archaeornithomimus, describe the many therizinosaur elements at the IVPP, describe the partial troodontid skeletons at the AMNH, etc..

Alectrosaurus olseni
(see page for materials list)
The lectotype hindlimb AMNH 6554) was discovered on April 25 1923 at Third Asiatic Expedition field site 136, while a partial forelimb (AMNH 6368) was found on May 4 at field site 138, 30 meters away.  Andrews (1932) first mention the former as "the complete hindlimb of a large carnivorous dinosaur.  The leg lay doubled up just as the great reptile had died millions of years ago."  Gilmore (1933) made each a syntype of his new taxon of deinodontid, Alectrosaurus olseni, noting "in the field they were thought to pertain to the same individual." but that he preferred to treat them as two individuals.  They were considered the same taxon based on the manual unguals (questionably associated in the case of AMNH 6554) "being laterally compressed, strongly curved, and having sharply pointed extremities", which are characters broadly true of almost all theropod manual unguals.  Barsbold (1976) was the first to consider AMNH 6368 wrongly assigned, stating "As new materials from the MPR* show, a large ungual phalanx previously attributed to the manus of Alectrosaurus (Gilmore, 1933) does not really belong to it" (translated), citing the still undescribed IGM 100/50 from Bayanshiree which includes "a small ungual phalanx of the first manual digit, quite typical for tyrannosaurids."  Further, he noted "A large, laterally compressed ungual phalanx, similar in structure and form to that attributed to Alectrosaurus, belongs to another previously unknown dinosaur (under study) found there. This dinosaur does not belong to Tyrannosauridae.", which is a reference to the also undescribed Segnosaurus.  In their redescription, Mader and Bradley (1989) describe AMNH 6368 in detail and place it in Segnosauridae, and it has been viewed as therizinosaurian since then.  As explained by Mader and Bradley, the type listing by White (1973) combined the syntype materials, so that Welles and Long (1974) officially declared the hindlimb as the lectotype when they stated "we here designate this specimen, AMNH 6554, the type of the species."  Zanno (2010: Fig. 9D) figured the manual unguals of AMNH 6554 as therizinosaurian without comment, although their non-tyrannosaurid characters could also be plesiomorphically shared with e.g. Dryptosaurus.
Dong et al. (1989) first reported Aublysodon from the July 1988 Sino-Canadian expedition (CCDP), and Currie et al. (1990) stated "Identical teeth [to Dinosaur Park juvenile tyrannosaurid 'Aublysodon'] recently were recovered from the Iren Dabasu Formation at Erenhot, People's Republic of China (IVPP 170788104). The Asian "Aublysodon" teeth belong to Alectrosaurus (Perle pers. comm. 1989..."  Similarly, Dong (1992) reports "In July 1988, the expedition of the CCDP came to Erenhot (Fig.85) where they collected ... teeth of ... large theropods (tyrannosaurid)."  Dong et al. first reported that in July 1988 "A partial skeleton of Alectrosaurus was discovered too late to collect", and Dong (1993) followed that up by writing "An incomplete skeleton of Alectrosaurus was found by Currie [in 1988], but was not excavated until the return expedition of 1990", which was at CCDP site #9 based on Currie and Eberth's (1993) table 3.  They further noted "Perle (1977) ... has been studying more recently discovered postcranial specimens (Perle, pers. comm. 1989)" and that "The absence of denticles on the premaxillary teeth (Perle, pers. comm. 1989; IVPP 180788-104) suggests that it should be included in the Aublysodontinae."   The similar field numbers to Currie et al.'s suggest one is a typo, and serrationless premaxillary teeth are a juvenile character of tyrannosaurines but also known in some basal tyrannosauroids (Yutyrannus, Xiongguanlong).  Currie (2001) reported "Several partial, undescribed skeletons of Alectrosaurus collected from southeastern Mongolia are in the collections of the museum in Ulaanbaatar, and another new specimen was recently collected from Erenhot in China", the latter seemingly being the one mentioned by Dong et al..
(see page for references)

undescribed tyrannosauroid (Granger and Berkey, 1922)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- (AMNH 6266; "AMNH 6556" of Carr, 2005) (small) incomplete lacrimal, anterior jugal, quadratojugal, lateral ectopterygoid, posterior pterygoid, premaxillary teeth, lateral teeth
Comments- Brochu (2003) noted "A box of bone fragments (AMNH 6266) from the same locality [as Alectrosaurus] includes small tyrannosaurid skull bones (including a characteristic jugal, lacrymal, quadratojugal, and D-shaped premaxillary tooth) that might belong to the same individual. ... The skull parts are consistent with Albertosaurus; for example, the jugal foramen is a dorsally-opening slit."  He states it "had been originally catalogued as "Deinodon sp." ..., but this was subsequently scratched off and "Theropoda indet." written on in pencil", and the AMNH online catalogue does list 6266 as "Deinodon ? sp."  Carr (2005) later reported "an undescribed, but shattered, tyrannosauroid skull (AMNH 6556) from the same general area - Iren Dabasu -" as the Alectrosaurus lectotype, but as they are from different locations "there is no evidence they are from the same individual."  Carr states "The presence of a secondary fossa in the antorbital fossa of the jugal indicates the specimen is referable to Tyrannosauridae. The cornual process of the lacrimal is similar to some juvenile tyrannosaurids in that it is a low, laterally extending ridge. The lateral teeth are as finely denticulate as tyrannosauroid teeth of the same basal crown length from the Turonian of Uzbekistan."  This is the "Iren Dabasu taxon" in Carr's tyrannosauroid analyses as of Carr et al. (2017), under study by Carr and recovered in a polytomy with Timurlengia, Jinbeisaurus and eutyrannosaurs as of 2019.  While this is certainly the same specimen based on material preserved, the AMNH online catalog lists this specimen number as being a saurischian metatarsal II with a locality "8 mi. E. of station" which would place it among Third Asiatic Expedition field sites 140-149 (while Alectrosaurus is from 136 less than a mile south of the station).  AMNH 6556 is listed in the catalogue as collected on April 30, which matches Carr's statement the skull was found in late April five days apart from Alectrosaurus' lectotype (which was found on April 25).  However, Mehling (pers. comm. 6-2022) indicates AMNH 6556 is actually a metatarsal II and that AMNH 6266 was discovered in 1922, so that Carr apparently got the specimen number wrong and incorrectly used the metatarsal's discovery date for the skull.  The early discovery makes sense considering the low specimen number and allows us to equate the material with  "portions of a small carnivorous dinosaur skull with two or three teeth" found in the 1922 expedition as reported by Granger and Berkey (1922) along with ornithomimid remains that are near certainly AMNH 6267-6268.  If it was recovered with the latter specimens, AMNH 6266 would have been found between April 25 and May 7 at one of the western AMNH quarries (131-138), and thus may be from the same locality the Alectrosaurus type as stated by Brochu.  Alas, the only recorded locality information in the AMNH card catalogue is Iren Dabasu (Mehling, pers. comm. 6-2022).
References- Granger and Berkey, 1922. Discovery of Cretaceous and older Tertiary strata in Mongolia. American Museum Novitates. 42, 7 pp.
Brochu, 2003. Osteology of Tyrannosaurus rex: Insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Society of Vertebrate Paleontology Memior. 7, 138 pp.
Carr, 2005. A reappraisal of tyrannosauroids from Iren Dabasu, Inner Mongolia, People's Republic of China. Journal of Vertebrate Paleontology. 25(3), 42A.
Carr, Varricchio, Sedlmayr, Roberts and Moore, 2017. A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Scientific Reports. 7:44942.

undescribed Tyrannosauridae (Gilmore, 1933)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- (AMNH 21552) (large) femur (Mader and Bradley, 1989)
(AMNH coll.) (large) pedal elements (Gilmore 1933)
(IVPP coll.) teeth and/or elements (Yao, Wang, Sullivan, Wang, Stidham and Xu, 2015)
Comments- Under Deinodontidae, Gilmore (1933) states "The presence of a second carnivore, apparently rivaling Tyrannosaurus in size, is indicated by a few scattered foot bones." These are no doubt one or more of the specimens listed here under undescribed Averostra (e.g. AMNH 6376, 6556, 6744, 6756, 6757, etc.).
Mader and Bradley (1989) noted "among the materials brought back by the Central Asiatic Expeditions was the isolated femur (AMNH 21552) of a much larger tyrannosaur [than the Alectrosaurus lectotype]."  This may belong to the same taxon as Gilmore's pedal material based on size.
Yao et al. (2015) note "small unarticulated bones and teeth, including fossils of ... tyrannosauroids" from "a rare microvertebrate locality within the Iren Dabasu Formation, about 16 km northeast of Erenhot City."
References- Gilmore, 1933. On the dinosaurian fauna of the Iren Dabasu Formation. Bulletin American Museum of Natural History. 67, 23-78.
Mader and Bradley, 1989. A redescription and revised diagnosis of the syntypes of the Mongolian tyrannosaur Alectrosaurus olseni. Journal of Vertebrate Paleontology. 9(1), 1-55.
Yao, Wang, Sullivan, Wang, Stidham and Xu, 2015. Caenagnathasia sp. (Theropoda: Oviraptorosauria) from the Iren Dabasu Formation (Upper Cretaceous: Campanian) of Erenhot, Nei Mongol, China. Vertebrata PalAsiatica. 53(4), 291-298.

Iren Dabasu ornithomimosaur pubes (left to right) - AMNH 21799 figured by Smith and Galton (1990) as Archaeornithomimus asiaticus so generally associated with the taxon; AMNH 21798 and a distal pubis in AMNH 6570, both among Archaeornithomimus material from the same bonebed as 21799; LH-02-01 from an unknown locality in the same area described by Yao et al. (2022) as Ornithomimosauria indet..  The first three are my photos courtesy of the AMNH (scale = 100 mm), the fourth is after Yao et al., 2022.

Archaeornithomimus asiaticus
(see page for materials list and additional comments)
Comments- Watanabe et al. (2015) state "Based on manual articulation of disarticulated sacral vertebrae, we identify the two sacral vertebrae (AMNH FARB 21790) sampled for this study as the second and third sacral vertebrae", but these are the second and third caudals as identified by Smith and Galton as confirmed by personal observation when sacrals 2-5 were on loan articulated to the ilium.  Similarly, two of the proximal caudals Watanabe et al. call AMNH 21790 are actually the last two vertebrae in AMNH 21802.
Other material- The AMNH catalog lists 6267 and 6268 as Ornithomimus sp., but they are probably Archaeornithomimus based on stratigraphy.  Given their lower specimen numbers, it is likely these were recovered in the initial reconnaissance expedition to Iren Dabasu in 1922 (April 25 to May 7) and represent the "Carnivorous dinosaurs of at least two genera, the smaller one being of the Ornithomimus type" reported by Granger and Berkey (1922).  Indeed, those authors later state "Remains of the small Ornithomimus-like creature are particularly abundant and the last day at Iren Dabasu we picked up probably fifty good foot bones and centra from two or three knolls", which matches the listed material.  The locality of AMNH 6267 is listed as "Iren Dabasu Sta. 1 1/2 SW of auto trail", so was plausibly from one of the western AMNH quarries (131-138), as opposed to the type material that was from the Kaisen Quarry (AMNH locality 140) and Johnson Quarry (AMNH locality 141) which were discovered the following year.  The AMNH online catalogue also lists AMNH 21626 and 21627 as possibly referrable to Archaeornithomimus. AMNH 21597 is figured as therizinosaurid ungual on the AMNH online catalog, but the low curvature and distally placed flexor tubercle are instead almost identical to Archaeornithomimus (e.g. AMNH 6570, 6576).  Currie and Eberth (1993) state "The present whereabouts of a partial skull found by the Sino-Soviet expedition is currently unknown", but their paper's details indicate it was found in June 1959 from their localities K (= AMNH locality 141?), L or P, and initially stored in either the IVPP or PIN. Chow and Rozhdestvensky (1960) specified the timing of excavations to be June 14 to July 17 and state "materials collected include ... small ornithopods (of Struthiomimus type)", with 'ornithopods' presumably a typo for 'theropods', and Currie and Eberth state "more than a thousand bones" were identified as ornithomimid in the filed from the Sino-Soviet expedition.  Currie and Eberth also say that after the joint BMNH - Inner Mongolian Museum expeditions of 1972-1977, "Some of the specimens (including ornithimimid ... skeletons) were prepared for display in Hohhot", with casts at the Erenhot Dinosaur Museum.  These were mostly from localities on the west side of Iren Nor.  Dong (1992) noted that "Archaeornithomimus is the most common species in the bone beds" where the CCDP excavated in July 1988 (and later in 1990), which would have ended up in the IVPP as no theropod body fossils from Iren Dabasu are at the TMP.  A distal caudal described by Makovicky (1995) as Avimimus "has the morphology of a typical coelurosaurian distal caudal, but is otherwise undiagnostic. The possibility that it may originate from an avimimid is suggested by its small size. It should be noted, however, that it could just as conceivably be from the tail of a juvenile Archaeornithomimus from the same bonebed."  Indeed, the A. nemegtensis bonebed show Avimimus has short distal caudals like other caenagnathoids and unlike ornithomimosaurs, so this specimen is here referred to Archaeornithomimus.  Godefroit et al. (1998) reported "one single ornithomimid caudal vertebra" from the Bactrosaurus bonebed they described from Locality SBDE 95E5, slightly to the west of AMNH locality 140.  Yao et al. (2015) note "small unarticulated bones and teeth, including fossils of ... ornithomimids" from "a rare microvertebrate locality within the Iren Dabasu Formation, about 16 km northeast of Erenhot City."
More than one taxon? There is non-ornithomimid material catalogued under Archaeornithomimus, including a juvenile ?Bactrosaurus ungual (in AMNH 6576), a small ?troodontid pedal ungual I (in AMNH 6576) and part of an ?oviraptorid manual ungual I (in AMNH 6570).
Yao et al. (2022) described pelvis and sacrum LH-02-01 discovered in 2002 from an undocumented locality near Iren Nor.  They added the specimen to Choiniere's coelurosaur analysis to recover it as an ornithomimosaur in a polytomy with Nqwebasaurus, Pelecanimimus, Shenzhousaurus, Beishanlong and Deinocheiridae+Ornithomimidae.  Supposed differences from Archaeornithomimus are- larger size (ilium 342 vs. 114 mm); "the shortest sacral centrum is the second rather than the third [actually the third instead of the fourth, assuming six sacrals as in Archaeornithomimus- Makovicky, 1995]; the centrum of the first caudal is shorter than that of the fifth [sixth] sacral"; first caudal with flat posterior articular surface vs. concave; first caudal with flat ventral surface vs. median groove; first caudal neural spine posteriorly sloped vs. vertical; pubic shaft straight vs. strongly posteriorly curved; transition between anterior pubic shaft and dorsal edge of pubic foot rounded vs. angled; anterior pubic foot more pointed; obturator process less prominent; ischial foot limited to anterior expansion vs. expanded some posteriorly; ischiopubic ratio 82% vs. 92%.  However, it seems the authors depended on the literature for their information on Archaeornithomimus (e.g. thinking the ischia are AMNH 21798 instead of 6558, and that the first caudal would be amphicoelous and grooved because Smith and Galton said in the proximal caudal paragraph "The centra are amphicoelous ... and each has a shallow ventral groove"), and this led to misinformation and incomplete statements.  Regarding size, there is an ilium ~380 mm long in AMNH 6570, larger than even LH-02-01.  The proximal five caudals of AMNH 21790 all lack median grooves ventrally and the posterior articular surface of the first centrum is still attached to a broken off part of the second centrum so cannot be evaluated.  The first caudal neural spine has been broken away since Smith and Galton's drawing, and the shape of the other neural spines differ from the drawing in greater to lesser degrees.  There is a distal pubis in AMNH 6570 with an almost identical foot to LH-02-01, including the rounded anterodorsal edge, more pointed anterior foot and shorter posterior foot.  Finally, there is no indication pubes AMNH 21799 and ischia AMNH 6558 were associated, and indeed five right proximal tibiae are known from site 140 that can differ in size ~10% from each other.  Thus sacra AMNH 21790 and LH-02-01 may be distinct based on central lengths, pubes AMNH 21799 and LH-02-01 / AMNH 6570 (in part) seem to be distinct, as do ischia AMNH 6558 and LH-02-01.  However, undescribed pubes AMNH 21798 are intermediate in having a slight anterior bow, rounded anterodorsal transition, less pointed anterior foot and intermediate posterior foot length.  This suggests the sacral and ischial differences could easily be due to the low sample size (N = 2) of each element and that considering all of these specimens to be conspecific is the most realistic and functional conclusion.  Since the lectotype is a partial pes not comparable to LH-02-01 at all (and without any proposed diagnosis or comparison to other Iren Dabasu ornithomimosaur pedal specimens), the other rational option would be to limit Archaeornithomimus asiaticus to AMNH 6565 and potentially other comparable specimens (e.g. AMNH 6568, 21616, 30240B/C and parts of 6570 and 6576) while leaving the non-pedal specimens as Ornithomimosauria indet..  Alternatively, LH-02-01 and e.g. AMNH 21790 or 6558 could be given names, but again the vast majority of specimens would be incomparable and relegated to Ornithomimosauria indet..  Given this data and pending the description of some of the multitude of unpublished specimens, all Iren Dabasu ornithomimosaurs are listed here under Archaeornithomimus asiaticus.
(see page for references)

unnamed therizinosaurid (Gilmore, 1933)
Middle-Late Campanian, Late Cretaceous
AMNH 138, Iren Dabasu Formation, Inner Mongolia, China
Material- (AMNH 6368; syntype of Alectrosaurus olseni) humerus (390 mm), manual ungual I (190 mm on curve), manual phalanx II-1 (74 mm)
?... (AMNH 21784) three mid caudal vertebrae (~41, ~38, ~35 mm), distal caudal centrum (~24 mm) (Mader and Bradley, 1989)
?... (uncollected) two or three elements (Mader and Bradley, 1989)
Comments- AMNH 6368 was found on May 4 1923 at Third Asiatic Expedition field site 138, 30 meters away from the lectotype of Alectrosaurus olseni and was thought to belong to the same individual in the field. Gilmore (1933) prefered to treat them as two individuals. He placed them in the same species due to the similarity between the manual unguals, which are “laterally compressed, strongly curved and have sharply curved extremities”, as well as the association in the field and slenderness. Gilmore originally diagnosed A. olseni partially on the characteristics of this specimen.  Rozhdestvensky (1970) recognized the similarity to Therizinosaurus and referred Alectrosaurus to Therizinosauridae, but Barsbold (1976) and Perle (1977) correctly removed the forelimb from that taxon based on supposed Alectrosaurus specimen IGM 100/50 with small humerus and manual ungual.  Mader and Bradley (1989) described the specimen in detail as a segnosaurid. Zanno (2010) notes the slender proportions, poorly defined medial tuberosity, and posterior humeral trochanter indicates it is not referable to Neimongosaurus, and it is more gracile than Erliansaurus and lacks that genus' distinctive crest-shaped posterior trochanter. Zanno (2006) recovered it as more derived than Alxasaurus in her phylogenetic analysis, and most recently Hartman et al. (2019) found it sister to Segnosaurus in Therizinosauridae.
AMNH 21784 was also discovered on May 4 1923 at Third Asiatic Expedition field site 138, but not catalogued until 1984 and not described until 1989 by Mader and Bradley. While those authors described them as Theropoda incertae sedis, they may be therizinosauroid based on their resemblence to Alxasaurus' mid caudals (e.g. short centra that become shorter distally; low neural spines; similarly placed transverse processes) although their neural spines are more posteriorly restricted and their prezygapophyses are longer.  Although Mader and Bradley considered the caudals too small to belong to the same individual as the humerus, they were comparing them to theropod proximal caudals as they were unaware of therizinosauroids' modified caudal series with relatively homogenous caudals decreasing in length distally.  In fact, given that Alxasaurus' holotype humerus is 4% longer than AMNH 6368, its fourteenth-eighteenth caudals are also slightly longer (39-44 mm) as is an isolated distal caudal (26 mm), so the sizes are appropriate to belong to a single therizinosauroid individual.  As they are from the same field site, that is provisionally accepted here.  Mader and Bradley also noted "two or three unspecified [theropod] elements that regrettably were not collected due to their "poor condition" (Granger's field record, Third Asiatic Expedition)" found with the forelimb and caudal material and might also belong to the same individual.
References- Gilmore, 1933. On the Dinosaurian Fauna of the Iren Dabasu Formation. Bulletin American Museum of Natural History. 67, 23-78.
Rozhdestvensky, 1970. Giant claws of enigmatic Mesozoic reptiles. Paleontological Journal. 1970(1), 131-141.
Barsbold, 1976. New data on Therizinosaurus (Therizinosauridae, Theropoda). In Kramarenko, Luvsandansan, Voronin, Barsbold, Rozhdestvensky, Trofimov and Reshetov (Eds.). Paleontology and Biostratigraphy of Mongolia. The Joint Soviet-Mongolian Paleontological Expedition, Transactions. 3, 76-92.
Perle, 1977. On the first discovery of Alectrosaurus (Tyrannosauridae, Theropoda) from the Late Cretaceous of Mongolia. Problemy Geologii Mongolii. 3, 104-113.
Mader and Bradley, 1989. A redescription and revised diagnosis of the syntypes of the Mongolian tyrannosaur Alectrosaurus olseni. Journal of Vertebrate Paleontology. 9(1), 41-55.
Zanno, 2006. The pectoral girle and forelimb of the primitive therizinosauroid Falcarius utahensis (Theropoda, Maniraptora): Analyzing evolutionary trends within Therizinosauroidea. Journal of Vertebrate Paleontology. 26(3), 636-650.
Zanno, 2010. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology. 8(4), 503-543.
Hartman, Mortimer, Wahl, Lomax, Lippincott and Lovelace, 2019. A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight. PeerJ. 7:e7247.

undescribed Therizinosauroidea (Dong, 1992)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- (Erenhot Dinosaur Museum coll.) dentary, teeth (Currie and Eberth, 1993)
(IVPP coll.) (isolated) many limb elements (Dong, 1992)
(IVPP and PIN coll.) tens of specimens (Cuirrie and Eberth, 1993)
Comments- Currie and Eberth (1993) stated "A rough tally of Sino-Soviet field identifications shows that ... 'theropods' (including large theropods, small theropods and segnosaurs, but not ornithomimids) were more common (400 specimens)" and that "The apparent high numbers of carnivorous dinosaurs can be attributed mostly to ornithomimids [>1000 elements] and segnosaurids" indicating some significant number of those 400 'theropods' found in June-July 1959 were therizinosaurs.
Dong (1992) reported "In July 1988, the expedition of the CCDP came to Erenhot (Fig.85) where they collected ... Many limb bones [which] might be identified as segnosaurs" and listed Segnosaurus sp. as being present in the formation.  He later (1993) said "at least two taxa of segnosaurs" were represented.  Currie and Eberth (1993) stated "isolated elements were commonly recovered by the Sino-Canadian expeditions in 1988 and 1990. A well-preserved dentary with teeth is in the collections of the Erenhot Dinosaur Museum. The isolated elements are indistinguishable from Erlicosaurus andrewsi and Segnosaurus ghalbiensis bones in the collections of the Paleontological Institute (at the Central State Museum) in Ulaan Baatar. There are a few elements from the Iren Dabasu that may also be referable to the more poorly known segnosaur Enigmosaurus."  They listed both Segnosaurus sp. and Erlikosaurus sp. as present, but given the poor state of knowledge of therizinosaur diversity in the early 90s, they may actually belong to the contemporaneous Erliansaurus, Neimongosaurus, and/or the taxon to which the forelimb AMNH 6368 belongs instead.  Precise localities have not been published, but the CCDP excavated several (Currie and Eberth, 1993: Table 3), all around Iren Nor and far from Sanhangobi where Erliansaurus and Neimongosaurus were found.
References- Dong, 1992. Dinosaurian Faunas of China: China Ocean Press. 188 pp.
Currie and Eberth, 1993. Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People’s Republic of China. Cretaceous Research. 14, 127-144.
Dong, 1993. The field activities of the Sino-Canadian Dinosaur Project in China, 1987-1990. Canadian Journal of Earth Sciences. 30(10), 1997-2001.

Kuszholia sp. (Yao, Wang, Sullivan, Wang, Stidham and Xu, 2015)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- (IVPP V20377) anterior dentaries (symph 8.0 mm)
Comments- This was discovered in 2012 at "a rare microvertebrate locality within the Iren Dabasu Formation, about 16 km northeast of Erenhot City", which would put it in localities Q-T of Xing et al. (2012).  Yao et al. (2015) referred IVPP V20377 to Caenagnathasia sp., and it does possess all characters here listed as diagnostic for that taxon.  Of their characters listed as varying between Caenagnathasia specimens, most also vary between Chirostenotes specimens (posterior surface of symphysis with tubercle; chin-like eminence between anterior and ventral surfaces; pneumatic foramen in front of mandibular fenestra on lateral surface of dentary; depression on posteroventral margin of symphysis [ontogenetic?]), while paired second anterior occlusal grooves flanking first anterior occlusal groove is polymorphic in the holotype, and lateral projections on lingual ridges may be absent in ZIN PH 2354/16 due to preservation.  This leaves presence of a median symphyseal groove on the posterodorsal depression in the holotype and IVPP V20377 but not ZIN PH 2354/16 (ontogenetic?) and on the posteroventral symphysis of IVPP V20377 but not the holotype or ZIN PH 2354/16 (taxonomic?).  The age difference suggests the specimen is not conspecific with the Bissekty species.
References- Xing, He, Li and Xi, 2012. A review on the study of the stratigraphy, sedimentology, and paleontology of the Iren Dabasu Formation, Inner Mongolia. In Dong (ed.). Proceedings of the Thirteenth Annual Meeting of the Chinese Society of Vertebrate Paleontology. China Ocean Press. 1-44.
Yao, Wang, Sullivan, Wang, Stidham and Xu, 2015. Caenagnathasia sp. (Theropoda: Oviraptorosauria) from the Iren Dabasu Formation (Upper Cretaceous: Campanian) of Erenhot, Nei Mongol, China. Vertebrata PalAsiatica. 53(4), 291-298.
Wang, Zhang and Yang, 2018. Reevaluation of the dentary structures of caenagnathid oviraptorosaurs (Dinosauria, Theropoda). Scientific Reports. 8:391.

Avimimus sp. nov. (Makovicky, 1995)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- (AMNH 6570 in part; paratype of Ornithomimus asiaticus) fibula (Chiappe, Norell and Clark, 2002)
(AMNH 6576 in part; paratype of Ornithomimus asiaticus) proximal caudal vertebra (Makovicky, 1995)
?(AMNH 6754) distal metatarsal III (Ryan, Currie and Russell, 2001)
?..?(AMNH 6755; 'AMNH 6555' of Funston, Currie, Ryan and Dong, 2019) incomplete metatarsus (mtII 100, mtIV 99 mm) (Ryan, Currie and Russell, 2001)
(AMNH 25569) caudal vertebra, ten vertebrae, three phalanges, five unguals including pedal ungual (~18 mm) (AMNH online)
(AMNH coll.) dorsal vertebrae (Makovicky, 1995)
?(IVPP V16313.a) manual ungual ?I (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16314; = TMP 1992.302.0102) proximal tarsometatarsus (Ryan, Currie and Russell, 2001)
?...(IVPP V16341) tarsometatarsus (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16315) metatarsal II (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16316.a) pedal ungual III (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16316.b) pedal ungual III (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16316.c; = TMP 1992.302.0119A) pedal ungual II/IV (Ryan, Currie and Russell, 2001)
(IVPP V16316.d; = TMP 1992.302.0119B) pedal ungual II/IV (Ryan, Currie and Russell, 2001)
(IVPP V16317.a) incomplete proximal caudal vertebra (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16317.b) mid caudal vertebra (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16318; ?= TMP 1992.302.0344) (juvenile) posterior cervical vertebra (Ryan, Currie and Russell, 2001)
(IVPP V16318.a) incomplete anterior dorsal vertebra (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16318.b; ?= IVPP 160788-124) incomplete posterior dorsal vertebra (Makovicky, 1995; Funston, Currie, Ryan and Dong, 2019)
(IVPP V16319) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16320) (<1 year old juvenile) distal tibiotarsus (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16321) proximal metatarsal II (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16322.a; = TMP 1992.302.0150) proximal tibia (Ryan, Currie and Russell, 2001)
(IVPP V16322.b) proximal tibia (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16322.c) proximal tibia (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16323.a) third dorsal vertebra (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16324) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16325) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16326) metatarsal II (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16327; = TMP 1992.302.0116) partial scapulocoracoid (Ryan, Currie and Russell, 2001)
(IVPP V16328) (juvenile) mid sacral centrum (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16329.a; = IVPP 180788-123) last or penultimate cervical vertebra (Makovicky, 1995)
(IVPP V16329.b) second dorsal vertebra (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16330; = IVPP 160788-122) posterior sacral fragment (Makovicky, 1995)
(IVPP V16331) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16332.a; = TMP 1992.302.0140) partial second dorsal vertebra (Ryan, Currie and Russell, 2001)
(IVPP V16332.b) partial first dorsal vertebra (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16333) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16334.a; = TMP 1992.302.0149) proximal femur (Ryan, Currie and Russell, 2001)
(IVPP V16335.a) (juvenile) distal tarsal IV fused to proximal metatarsal IV (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16335.b) distal metatarsal II/III
....(IVPP V16335.c) distal metatarsal II/III
....(IVPP V16336) distal metatarsal IV
(IVPP V16337) (>2 year old adult) distal tarsometatarsus (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16338; = TMP 1992.302.0110) distal femur (Ryan, Currie and Russell, 2001)
(IVPP V16339) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16340; = TMP 1992.302.0117) proximal humerus (Ryan, Currie and Russell, 2001)
?(IVPP V16342; = TMP 1992.302.0104) partial frontal (Ryan, Currie and Russell, 2001)
(IVPP V16343) distal metacarpal I (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16344) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V16345) some of "IVPP V163.." below (Funston, Currie, Ryan and Dong, 2019)
(IVPP V163...) four dorsal vertebrae, distal metatarsal, pedal ungual III, eight pedal unguals II/IV (Makovicky, 1995; Funston, Currie, Ryan and Dong, 2019)
(PIN coll.) material (Currie and Eberth, 1993)
Diagnosis- (after Funston et al., 2019) three cervicodorsal vertebrae (unknown in A. nemegtensis); deeper femoral intercondylar groove.
Comments- Makovicky (1995) stated "Avimimid vertebrae were collected by the American Museum Central Asian expedition in 1922 at Iren Dabasu. However, they were not recognised as such, and were catalogued with Ornithomimus asiaticus (now Archaeornithomimus asiaticus) material", but the Archaeornithomimus type material was discovered in 1923 including a proximal caudal referenced by the author.  While he says "one of the caudals collected by the American Museum's Central Asiatic Expeditions (AMNH 6576), [has] a small pointed tubercle separates the ventromedial corners of the chevron facets" this specimen number includes almost a hundred elements from the Johnson Quarry AMNH locality 141 generally referred to Archaeornithomimus.  A fibula (AMNH 6570) was figured as "alvarezsaurid fibula from Iren Dabasu (Inner Mongolia, China)" by Chiappe et al. (2002), but Longrich and Currie (2009) stated "it more closely resembles the fibula of Avimimidae, which are common at this locality (N.R.L., pers. obs.)."  Again this number includes over two hundred paratype Archaeornithomimus elements, this time from the Kaisen Quarry AMNH locality 140.  Makovicky also stated "A large number of dorsal vertebrae are present in the American Museum ... collections from Iren Dabasu", which are likely to also be catalogued under AMNH 6570 and/or 6576.  Longrich's claim is supported here however as the fibula has an anteriorly projected iliofibularis tuber as in Avimimus but unlike the laterally directed tuber of e.g. IGM 100/99 and is less reduced distally in anteroposterior width than the latter.  A distal caudal (AMNH coll.) described by Makovicky "has the morphology of a typical coelurosaurian distal caudal, but is otherwise undiagnostic. The possibility that it may originate from an avimimid is suggested by its small size. It should be noted, however, that it could just as conceivably be from the tail of a juvenile Archaeornithomimus from the same bonebed."  Indeed, the A. nemegtensis bonebed show Avimimus has short distal caudals like other caenagnathoids and unlike ornithomimosaurs, so this specimen is here referred to Archaeornithomimus.  The AMNH online catalogue lists AMNH 25569 as "10 vertebrae 1 caudal vertebra 3 phalanges & 5 claws" of Saurischia from the Johnson Quarry with a pedal ungual photographed as Avimimidae.  A metatarsus (AMNH 6755) and third metatarsal (AMNH 6754) were listed on the museum's online catalogue as Elmisaurus sp., but also referred to Avimimus by Ryan et al. (2001) and Funston et al. (for AMNH 6755 at least).  Ryan et al.'s poster indicated both were found in 1923 and were possibly associated.  AMNH 6755 does seem smaller than other fused Avimimus and less slender, so further study is necessary.  Note Funston et al. (2019) describe and figure this as AMNH 6555, which is the number of ornithischian material.  Funston et al. state the main Iren Dabasu Avimimus bonebed "was originally discovered by a Sino-Soviet expedition in 1959, which used bulldozers to excavate the site. It was revisited in 1987 and 1988 by the Sino-Canadian expedition and numerous fragmentary bones representing all regions of the skeleton (Fig. 2) were recovered from the spoil piles left by the Sino-Soviet bulldozers. Unfortunately, the material collected by the Sino-Soviet expedition still awaits preparation and it may never be available for study."  This indicates it must be locality K of Currie and Eberth (1993), which was CCDP locality 1 and may correspond to AMNH locality 141.  One element from this excavation was described and figured by Kurzanov (1987) as "a left avimimid femur from the Upper Cretaceous Iren-Nor locality in China (specimen PIN, no. 2549-100)" (translated) but is here placed in Oviraptoridae.  While the PIN Sino-Soviet Avimimus material remains undescribed (although mentioned by Currie and Eberth), the Sino-Canadian material was noted by Dong et al. (1989) who reported "seven pedal elements of Avimimus" discovered  in July 1988 and Dong (1992) refers to "fused tarsometatarsi of Avimimus" recovered on that expedition in July 1998.  Currie and Eberth (1993) stated "Direct comparison between isolated Avimimus bones from the Iren Dabasu and the type specimen of Avimimus portentosus in Moscow failed to reveal any differences" and said the "material is presently under review (Currie, Zhao and Kurzanov, in preparation)."  The Sino-Canadian Avimimus material was eventually described by Makovicky, Ryan et al., then officially by Funston et al. as Avimimus sp..   Makovicky used IVPP field numbers (of which IVPP 180788-123 may be a mistake for IVPP 160788-123 to better match the other two listed numbers and only differ in the last digit), Ryan et al. used TMP numbers in their poster, and the specimens were seemingly eventually transported back to the IVPP for permanent storage.  Note the "isolated left frontal" mentioned by Sues et al. is not described in Funston et al. (although the frontal is highlighted as preserved in their figure 2), but Funston (2019) describes it in his thesis chapter that was developed into that paper.  In it he says "whether it pertains to an avimimid or another oviraptorosaur is uncertain. It can be distinguished from other theropods by the large, incising nasal contact, which is similar to the morphology of Elmisaurus rarus", so it's possible this belonged to the Iren Dabasu caenagnathid taxon represented by dentaries IVPP V20377.  IVPP 160788-124 is one of three posterior dorsals without a ventral keel, so may be IVPP V16318.b which was the only one of these figured by Funston et al..  Another tricky specimen is TMP 1992.302.0344 as illustrated in Ryan et al.'s poster, which is tentatively identified as posterior cervical IVPP V16318 as it seems to have a ventrally placed parapophysis, an elongate centrum with vertical articular surfaces, two or three central foramina and a dark neurocentral boundary perhaps representing an open suture, but contra to Funston et al.'s description is not notably smaller than other cervicals.  While Funston et al. only referred to the Iren Dabasu material as Avimimidae gen. et sp. indet., they also stated "the cervicodorsal vertebrae differ in number (three with hypapophyses) from those of Avimimus portentosus (MPC-D 100/129), although cervicodorsal number in Avimimus nemegtensis is unknown. The distal condyles of the femur (Fig. 6) are separated much more deeply than is typical in avimimids, and metatarsals II and IV (Fig. 8) are much more disparate in size", but ended up concluding "the available material from the Iren Dabasu bonebed is too incomplete to confidently erect a new taxon, but future preparation of the Russian material (or collection of new material) may result in its taxonomic distinction from other avimimids."
References- Kurzanov, 1987. Avimimidae and the problem of the origin of birds. Trudy, Sovmestnaa Sovetsko-Mongolskaa paleontologiceskaa ekspedicia. 31, 1-95.
Dong, Currie and Russell, 1989. The 1988 field program of the Dinosaur Project. Vertebrata Palasiatica. 27(3), 233-236.
Dong, 1992. Dinosaurian Faunas of China. China Ocean Press. 188 pp.
Currie and Eberth, 1993. Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People's Republic of China. Cretaceous Research. 14, 127-144.
Makovicky, 1995. Phylogenetic aspects of the vertebral morphology of Coelurosauria (Dinosauria: Theropoda). Masters thesis, University of Copenhagen. 311 pp.
Ryan, Currie and Russell, 2001. New material of Avimimus portentosus (Theropoda) from the Iren Dabasu Formation (Upper Cretaceous) of the Erenhot region of Inner Mongolia. Journal of Vertebrate Paleontology. 21(3), 95A.
Chiappe, Norell and Clark, 2002. The Cretaceous, short-armed Alvarezsauridae, Mononykus and its kin. In Chiappe and Witmer (eds.). Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press. 87-120.
Longrich and Currie, 2009 (online 2008). Albertonykus borealis, a new alvarezsaur (Dinosauria: Theropoda) from the Early Maastrichtian of Alberta, Canada: Implications for the systematics and ecology of the Alvarezsauridae. Cretaceous Research. 30(1), 239-252.
Funston, 2019. Anatomy, systematics, and evolution of Oviraptorosauria (Dinosauria, Theropoda). PhD thesis, University of Alberta. 774 pp.
Funston, Currie, Ryan and Dong, 2019. Birdlike growth and mixed-age flocks in avimimids (Theropoda, Oviraptorosauria). Scientific Reports. 9:18816. 

Small portion of material catalogued under AMNH 6570 and assigned to Archaeornithomimus.  Note the ungual in the upper left is not ornithomimid and here compared favorably to Citipati.  My photo courtesy of the AMNH.

cf. Citipati (Kurzanov, 1987)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- ?(AMNH 6570 in part; paratype of Ornithomimus asiaticus) partial manual ungual ?I (~39 mm) (pers. obs.)
(PIN 2549-100) femur (~160 mm) (Kurzanov, 1987)
Comments- Kurzanov (1987) briefly described and figured "a left avimimid femur from the Upper Cretaceous Iren-Nor locality in China (specimen PIN, no. 2549-100)" (translated), which Currie and Eberth (1993) indicate was found by the Sino-Soviet expedition, which means it was collected between June 14 and July 17 at their localities K (= AMNH locality 141?), L or P.  Kurzanov referred it to Avimimidae based on the "accessory condyle" (which is just the lateral condyle being separated from the ectocondylar tuber by a fibular groove as in most theropods), the broad intercondylar flexor groove and similarities of the trochanteric crest.  Indeed, he stated "the only not very significant difference is expressed in the fusion of the large and small trochanters, while in Avimimus they are separated by a narrow gap."  On the other hand, Osmolska (1996) stated "There is a great resemblance between the femur in [Bagaraatan] ostromi and the femur PIN 2549-100" in that "Both femora have similarly shaped proximal and distal ends, ... well pronounced articular heads and femoral necks, the poorly delimited lesser trochanters, which are as high as the greater, and in the presence of the protuberances on the lateral surface."  Additionally, "The distal ends of femora are also similarly shaped in both compared forms" with "distinctive tibiofibular crests ('condylus lateralis' in Kurzanov 1987)."  While PIN 2549-100 is similar in shape to both Iren Dabasu Avimimus and Bagaraatan, the latter both have accessory trochanters (usually misidentified as a large, distally placed anterior trochanter in Avimimus) which are absent in PIN 2549-100, Avimimus differs from PIN 2549-100 and Bagaraatan in lacking a distal ectocondylar notch defining the tuber, Bagaraatan differs from PIN 2549-100 and Avimimus in having a narrow flexor groove, and PIN 2549-100 differs from at least Avimimus in having a fourth trochanter reduced to "a slight roughness, located almost under the head of the femur on its medial side" (Kurzanov, 1987) (unknown in Bagaraatan).  Currie and Eberth (1993) believed PIN 2549-100 "is probably from a troodontid" and "provisionally referred to Saurornithoides", but Averianov and Sues (2012) concluded it "is probably troodontid but cannot be definitely referred to Saurornithoides" and "should be listed as Troodontidae indet."  However, scoring this in Hartman et al.'s maniraptoromorph analysis results in identical scorings to Citipati osmolskae, with one more step needced to move it sister to Avimimus and two more to move it to Troodontidae (as sister to Linhevenator).  Given the stratigraphic and geographic proximity, it is provisionally assigned to cf. Citipati here pending description of the holotype's femur (IGM 100/979 and 1004 have crushed and poorly exposed femora).
The hypodigm of Archaeornithomimus asiaticus includes two collections of largely undescribed and unassociated specimens, AMNH 6570 from Third Asiatic Field site 140 and AMNH 6576 from site 141, discovered between April 22 and May 25 1923.  Based on personal examination (July 2009), multiple elements in these collections do not belong to Archaeornithomimus, among which is an ungual in a box of phalanges and calcanea under AMNH 6570.  It is moderately curved with a large, proximally placed flexor tubercle and resembles both Sinornithoides' pedal ungual I and Citipati's manual ungual I in its preserved portion. As it is twice the length of Iren Dabasu's troodontid pedal unguals I but scales well to PIN 2549-100, the latter identification is provisionally preferred here.
References- Kurzanov, 1987. Avimimidae and the problem of the origin of birds [in Russian]. Trudy, Sovmestnaa Sovetsko-Mongolskaa paleontologiceskaa ekspedicia. 31, 1-95.
Currie and Eberth, 1993. Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People's Republic of China. Cretaceous Research. 14, 127-144.
Osmolska, 1996. An unusual theropod dinosaur from the Late Cretaceous Nemegt Formation of Mongolia. Acta Palaeontologica Polonica. 41, 1-38.
Averianov and Sues, 2012. Correlation of Late Cretaceous continental vertebrate assemblages in middle and central Asia. Journal of Stratigraphy. 36(2), 462-485.

undescribed Troodontidae (Currie and Eberth, 1993)
Middle-Late Campanian, Late Cretaceous
Erenhot, Iren Dabasu Formation, Inner Mongolia, China
Material- (AMNH 6570 in part; paratype of Ornithomimus asiaticus) (juvenile or subadult) axis, third cervical vertebra, fifth cervical vertebra (Makovicky, 1995)
?(AMNH 6576 in part; paratype of Ornithomimus asiaticus) pedal ungual I (~17 mm) (pers. obs.)
(AMNH 21751) distal metatarsals III (Currie and Eberth, 1993)
(AMNH 21772) metatarsal II (~183 mm) (Currie and Eberth, 1993)
(AMNH 25570) three vertebrae (AMNH online)
(AMNH 30261) proximal metatarsal (AMNH online)
(AMNH 30262) proximal tibial fragment (AMNH online)
(AMNH 30263) proximal tibial fragment (AMNH online)
(AMNH 30264) tibial fragment, fibular fragment (AMNH online)
(AMNH 30265) proximal tibia (AMNH online) 142
(AMNH 30266) proximal fibula (AMNH online) 142
(AMNH 30267) proximal tibia (AMNH online)
(AMNH 30268) proximal fibula (AMNH online)
(AMNH 30269) proximal fibula (AMNH online) 142
(AMNH 30270) proximal fibula (AMNH online)
(AMNH 30271) partial astragalus (AMNH online)
(AMNH 30272) partial astragalus (AMNH online)
(AMNH 30273) partial astragalus (AMNH online)
(AMNH 30274) partial astragalus (AMNH online)
(AMNH 30275) distal humerus (AMNH online)
(AMNH 30276) distal humerus (AMNH online)
(AMNH 30277) distal humerus (AMNH online)
(AMNH 30278) proximal humerus (AMNH online)
(AMNH 30279) proximal humerus (AMNH online)
(AMNH 30280) proximal ulna (AMNH online)
(AMNH 30281) distal radius (AMNH online)
(AMNH 30282) distal radius (AMNH online)
(AMNH 30283) proximal scapula (AMNH online)
(AMNH 30284) proximal scapula (AMNH online)
(AMNH 30285) scapular blade (AMNH online)
(AMNH 30286) pedal ungual I (~19 mm) (AMNH online)
(AMNH 30287) proximal manual ungual (AMNH online)
(AMNH 30288) two posterior cervical or proximal caudal vertebrae (AMNH online)
(AMNH 30289) distal metatarsal IV (AMNH online)
(AMNH 30290) distal metatarsal IV (AMNH online)
(AMNH 30291) distal metatarsal IV (AMNH online)
(AMNH 30292) distal metatarsal III (AMNH online)
(AMNH 30293) distal metatarsal III (AMNH online)
(AMNH 30294) distal metatarsal II (AMNH online)
(AMNH 30295) distal metatarsal II (AMNH online)
(AMNH 30296) distal metatarsal II (AMNH online)
(AMNH 30297) distal metatarsal II (AMNH online)
(AMNH 30300) partial ilium (AMNH online) 142
(AMNH 30301) proximal ?pubis (AMNH online) 142
(AMNH 30302) ?ilial fragment (AMNH online)
(AMNH 30303) partial synsacrum (AMNH online) 142
(AMNH 30304) proximal ?pubis (AMNH online)
?(AMNH 30305) last sacral vertebra (~25 mm) (AMNH online)
(AMNH 30306) partial synsacrum (AMNH online)
(AMNH 30307) synsacral fragment(AMNH online)
(AMNH 30308) partial posterior cervical vertebra (AMNH online)
(AMNH 30309) partial posterior cervical vertebra (AMNH online)
(AMNH 30310) partial anterior dorsal vertebra (AMNH online)
(AMNH 30311) partial anterior dorsal vertebra (AMNH online)
(AMNH 30312) partial anterior dorsal centrum (AMNH online)
(AMNH 30313) incomplete anterior dorsal centrum (AMNH online)
(AMNH 30314) partial anterior dorsal centrum (AMNH online)
(AMNH 30315) incomplete anterior dorsal centrum (AMNH online)
(AMNH 30316) partial anterior dorsal vertebra (AMNH online)
(AMNH 30317) incomplete anterior dorsal centrum (~24 mm) (AMNH online)
(AMNH 30318) anterior dorsal centrum (~26 mm) (AMNH online)
(AMNH 30320) anterior dorsal centrum (~26 mm) (AMNH online) 142
(AMNH 30321) partial anterior dorsal vertebra (~26 mm) (AMNH online)
?(AMNH 30322) anterior dorsal centrum (~32 mm) (AMNH online)
(AMNH 30323) incomplete posterior dorsal centrum (~22 mm) (AMNH online)
(AMNH 30324) incomplete dorsal centrum (AMNH online)
(AMNH 30325) posterior dorsal centrum (~26 mm) (AMNH online)
(AMNH 30326) posterior dorsal centrum (~27 mm) (AMNH online)
(AMNH 30327) posterior dorsal centrum (~27 mm) (AMNH online)
(AMNH 30328) incomplete posterior dorsal vertebra (~27 mm) (AMNH online)
(AMNH 30329) incomplete posterior dorsal vertebra (~29 mm) (AMNH online)
(AMNH 30330) proximal caudal centrum (~23 mm) (AMNH online)
(AMNH 30336) ?central fragment (AMNH online)
(AMNH 30337) incomplete distal caudal vertebra (~35 mm) (AMNH online)
(AMNH 30338) mid caudal vertebra (~32 mm) (AMNH online)
(AMNH 30339) incomplete mid caudal vertebra (~31 mm) (AMNH online)
(AMNH 30340) incomplete mid caudal vertebra (AMNH online)
(AMNH 30341) partial distal caudal vertebra (AMNH online)
(AMNH 30342) mid caudal vertebra (~29 mm) (AMNH online)
(AMNH 30343) mid caudal vertebra (~30 mm) (AMNH online)
(AMNH 30344) distal caudal vertebra (~32 mm) (AMNH online)
(AMNH 30345) incomplete mid caudal vertebra (~25 mm) (AMNH online)
(AMNH 30346) partial distal caudal vertebra (AMNH online)
(AMNH 30347) partial distal caudal vertebra (AMNH online)
(AMNH 30348) distal caudal vertebra (~31 mm) (AMNH online)
(AMNH 30349) fragmentary distal caudal vertebra (AMNH online)
(AMNH 30350) distal caudal vertebra (~33 mm) (AMNH online)
(AMNH 30351) incomplete distal caudal vertebra (~31 mm) (AMNH online)
(AMNH 30352) partial distal caudal vertebra (AMNH online)
(AMNH 30353) incomplete distal caudal vertebra (AMNH online)
(AMNH 30354) distal caudal vertebra (~23 mm) (AMNH online)
?(AMNH 30355) mid caudal vertebra (~32 mm) (AMNH online)
(AMNH 30356) proximal caudal centrum (~28 mm) (AMNH online)
(AMNH 30357) incomplete proximal caudal vertebra (~25 mm) (AMNH online)
(AMNH 30358) proximal caudal vertebra (~24 mm) (AMNH online)
(AMNH 30359) incomplete proximal caudal centrum (AMNH online)
(IVPP 230790-16; = IVPP 230090-16 of Currie and Eberth, 1993) metatarsal III (Currie and Eberth, 1993)
Comments- Currie and Eberth (1993) stated "Troodontid bones are rare, but include distinctive third metatarsals (AMNH 21751, 21772, IVPP 230090-16), in which the distal articulation extends onto the posterior surfrace of the bone in a broad tongue."  However, Currie and Dong (2001) corrected the identification of the second specimen, stating "AMNH 21772 is the proximal end of a second metatarsal. It is identified as a troodontid on the basis of its contact surface for the fourth metatarsal, its size, and especially its lateromedial compression."  The AMNH online catalogue photo indicates most of the element is preserved and the locality info is "8 mi. E. of station" indicating it was found in localities 140-149 in 1923 or 1928.  Currie and Dong describe AMNH 21751 as "two distal ends of third metatarsals [that] are about the same size and represent left and right elements. Although they may represent the same individual, the two fossils are different colours, which suggests they may not have been found together."  They indicate these were "Collected in the 1920s by the third Central Asiatic Expedition from exposures of the Iren Dabasu Formation (?Santonian) near Erenhot."  Currie and Dong list IVPP 230790-16 (presumably the correct field number for Currie and Eberth's 'IVPP 230090-16') as a metatarsal "Collected in 1990 from exposures of the Iren Dabasu Formation (?Santonian) near Erenhot", which would make it found during the second Sino-Canadian expedition.  They state "the tongue-like extensions of the third metatarsals from Iren Dabasu are flat like those of Troodon ... , Borogovia ... , and Tochisaurus" but unlike the grooved surface of Sinornithoides or the distally restricted surface of Philovenator.  This has since been identified in Bissekty Urbacodon sp. ZIN PH 2342/16, and it should be noted the extension of Tochisaurus is much shorter, while Mei, IGM 100/44, 100/140 and 100/1126 have a condition like Sinornithoides.  Thus as hypothesized by Dong and Currie, at least AMNH 21751 and IVPP 230790-16 are closer to Troodon than Sinornithoides.  Currie and Eberth stated "These bones are provisionally referred to Saurornithoides" (at the time a concept including Zanabazar) without rationale, but Currie and Dong instead classified them as "an unknown species of troodontid", stating they "cannot be identified further without additional material."
Makovicky (1995) stated "A probable troodontid axis (AMNH 6570), articulated with a third cervical vertebra, is present in the collections of the American Museum of Natural History. This identification is based on the morphology of the associated third cervical and a probable fifth cervical, possibly from the same individual, which strongly resembles those of Troodon. The axis is from an immature individual as seen from absence of both the odontoid and axial intercentrum."  This specimen number includes over two hundred paratype Archaeornithomimus elements from the Kaisen Quarry AMNH locality 140, and the cervicals described were not recognized in the material catalogued under it in July 2009 (pers. obs.).  However, a small ungual was noticed in AMNH 6576 (which includes almost a hundred paratype Archaeornithomimus elements from the Johnson Quarry AMNH locality 141) that most closely resembles a troodontid pedal ungual I in the slight curvature, proximally placed flexor tubercle and posterodorsal extent being less than its posteroventral extent.
The AMNH online catalogue lists AMNH 25570 as "Troodon ?", consisting of "3 vertebrae."  A large number of elements (AMNH 30261-30297, 30300-30318, 30320-30330, 30336-30359) are labeled are labeled "Troodontid" on the AMNH online catalogue, each from the same location ("8 mi. E. of station") and from AMNH Quarry 142 specifically when visible in the photo (AMNH 30265, 30266, 32069, 30300, 30301, 30303, 30320).  Given the similar preservation and number of elements preserved, it is possible these represent two individuals, and that several other specimens only identified to the level of Saurischia in the online catalogue (AMNH 30245, 30247-30260, 30298-30299, 30360) that are also from "8 mi. E. of station" may belong to them as well.  Note AMNH 30267 is incorrectly identified as a proximal fibula, while 30288 is called "Proximal end of metatarsal IV" but seems to be two vertebrae instead, AMNH 30301 is called an "Ilium fragment." but may be a proximal pubis (posterior edge downward in photo), AMNH 30302 is labeled as "Acetabulum fragment." and indeed may be the ischial peduncle and postacetabular base of a left ilium, AMNH 30304 is labeled "Prox. end of ischium" but more closely resembles a proximal troodontid pubis in the diverging peduncles and shallowly concave acetabular edge, AMNH 30305 is a last sacral vertebra with a convex posterior central face and 30322 is an anterior dorsal with convex anterior central face so both may be alvarezsaurid instead.  Scoring the material as photographed in the online catalogue (with AMNH 30305 and 30322 excluded, and 30301 and 30304 interpreted as pubes) into Hartman et al.'s maniraptoromorph matrix does result in it being troodontid, but note examination of the specimens themselves would provide far more data for each element and that it's currently only an assumption that they belong to the same taxon.
References- Currie and Eberth, 1993. Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People's Republic of China. Cretaceous Research. 14, 127-144.
Makovicky, 1995. Phylogenetic aspects of the vertebral morphology of Coelurosauria (Dinosauria: Theropoda). Masters thesis, University of Copenhagen. 311 pp.
Currie and Dong, 2001. New information on Cretaceous troodontids (Dinosauria, Theropoda) from the People's Republic of China. Canadian Journal of Earth Sciences. 38(12), 1753-1766.
Averianov and Sues, 2012. Correlation of Late Cretaceous continental vertebrate assemblages in middle and central Asia. Journal of Stratigraphy. 36(2), 462-485.

Sample of unguals catalogued under AMNH 6576 as Archaeornithomimus.  The bottom left one is not ornithomimid and is compared to pedal ugual I of Sinornithoides here, so suggested to be troodontid.  Note too the juvenile ?Bactrosaurus pedal ungual in the box on the right.  Scale = 100 mm.  My photo courtesy of the AMNH.

undescribed Dromaeosauridae (Gilmore, 1933)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- (AMNH 6572) pedal phalanx II-1 (Ostrom, 1969)
(AMNH 21781) pedal ungual II (AMNH online)
?(IVPP 270790-4) tooth (~21x~9x? mm) (Currie and Zhao, 1993)
?(IVPP V16334.b) proximal femur (Funston, Currie, Ryan and Dong, 2019)
(IVPP coll.) teeth, elements (Dong, Currie and Russell, 1989)
(IVPP coll.) teeth and/or elements (Yao, Wang, Sullivan, Wang, Stidham and Xu, 2015)
Comments- Gilmore (1933) noted the presence of "a few foot bones and other fragmentary skeletal parts" of small theropods from the Iren Dabasu Formation that he assigned to "Dromaeosaurinae Genus and species indet.", but admitted that this assignment as opposed to Coeluridae or Compsognathidae is based purely on their Cretaceous age.  Thus while it turned out at least two of these elements are apparently dromaeosaurid (see below), Gilmore's rationale is equivalent to Maniraptora indet. today and the fossils referenced plausibly included material now recognized as avimimid, troodontid and ?alvarezsaurid.  Ostrom (1969) noted in a discussion of deinonychosaur pedal examples that "E. H. Colbert has also discovered an isolated phalanx (AMNH 6572) in the American Museum collections from the Iren Dabasu Formation of Mongolia which compares almost exactly with the proximal phalanx of digit II of Deinonychus, but is perhaps 20 percent larger", which would make it somewhere around 46-52 mm long.  He shows it questionably derived from Velociraptor in his phylogram without explanation, which would not make sense in the most recent interpretation of Iren Dabasu's age being contemporaneous or slightly older than the Djadochta.  Paul (1988) states "at the AMNH is a hyper-extendable toe bone from the Late Cretaceous of Mongolia that looks like a Velociraptor somewhat bigger than V. antirrhopus [= Deinonychus]", but it is uncertain whether he saw it independant of Ostrom's text (Paul, pers. comm. 6-2022).  The AMNH online catalogue lists AMNH 21781 as an Iren Dabasu member of Dromaeosauridae represented by "Ungual of pes (digit II)" and being found by Kaisen.  Both AMNH 6572 and 21781 would have been found in Erenhot during the April 22 to May 25 1923 Central Asiatic Expedition.
Dong et al. (1989) state Velociraptor material was discovered in the July 1988 Sino-Canadian expedition to Erenhot, and Dong (1992) specifies "teeth of Velociraptor".  Currie and Eberth (1993) state "Isolated dromaeosaurid teeth and bones are common in the Iren Dabasu" and that "Most of these can be attributed to Velociraptor, although some of the teeth suggest that there was a second, larger species of an indeterminate dromaeosaurine dromaeosaurid."  Yet no rationale was presented, and the only two specified Iren Dabasu dromaeosaurid elements in the literature are clearly not Velociraptor (AMNH 6572 is twice the size, while IVPP 270790-4 is different from most dromaeosaurid teeth as noted above). AMNH 6572 may belong to the supposed dromaeosaurine though, based on size.  Currie and Zhao (1993) figure "Dromaeosaurid tooth (IVPP 270790-4) from the Iren Dabasu Formation near Erenhot, People's Republic of China, showing replacement pit on medial side of root", but given the slight constriction basal to the crown, convex distal edge and seeming lack of serrations, this may be misidentified.  Based on its similar field number to troodontid metatarsal IVPP 230790-16 it was probably also found in the Sino-Canadian expedition of 1990.
Funston et al. (2019) notes a femoral head that supposedly differs from Avimimus in having fused anterior and greater trochanters, "which suggests that it may be oviraptorid or, more likely, dromaeosaur."  This is from the Avimimus bonebed (locality K of Currie and Eberth [1993], which was CCDP locality 1 and may correspond to AMNH locality 141) and recovered in July 1988.  Interestingly, femur PIN 2549-100 is from the same locality and shares a trochanteric crest, but is here identified as oviraptorid.  It's possible they are from the same taxon (or even individual).
Yao et al. (2015) note "small unarticulated bones and teeth, including fossils of ... dromaeosaurids" from "a rare microvertebrate locality within the Iren Dabasu Formation, about 16 km northeast of Erenhot City."
References- Gilmore, 1933. On the dinosaurian fauna of the Iren Dabasu Formation. Bulletin American Museum of Natural History. 67, 23-78.
Ostrom, 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum of Natural History Bulletin. 30, 1-165.
Paul, 1988. Predatory Dinosaurs of the World. Simon & Schuster. 464 pp.
Dong, Currie and Russell, 1989. The 1988 field program of The Dinosaur Project. Vertebrata PalAsiatica. 27(3), 233-236.
Dong, 1992. Dinosaurian Faunas of China. China Ocean Press. 188 pp.
Currie and Eberth, 1993. Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People s Republic of China. Cretaceous Research. 14, 127-144.
Currie and Zhao, 1993 (published 1994). A new troodontid (Dinosauria, Theropoda) braincase from the Dinosaur Park Formation (Campanian) of Alberta. Canadian Journal of Earth Sciences. 30(10-11), 2234-2247.
Yao, Wang, Sullivan, Wang, Stidham and Xu, 2015. Caenagnathasia sp. (Theropoda: Oviraptorosauria) from the Iren Dabasu Formation (Upper Cretaceous: Campanian) of Erenhot, Nei Mongol, China. Vertebrata PalAsiatica. 53(4), 291-298.
Funston, Currie, Ryan and Dong, 2019. Birdlike growth and mixed-age flocks in avimimids (Theropoda, Oviraptorosauria). Scientific Reports. 9:18816.

undescribed possible dromaeosaurine (Currie and Eberth, 1993)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- teeth
Comments- Currie and Eberth (1993) state "Isolated dromaeosaurid teeth and bones are common in the Iren Dabasu" and that "Most of these can be attributed to Velociraptor, although some of the teeth suggest that there was a second, larger species of an indeterminate dromaeosaurine dromaeosaurid."  A pedal phalanx II-1 (AMNH 6572) mentioned by Ostrom (1969) as being 20% larger than Deinonychus may belong to the same taxon, based on size.
References- Ostrom, 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum of Natural History Bulletin. 30, 1-165.
Currie and Eberth, 1993. Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People s Republic of China. Cretaceous Research. 14, 127-144.

undescribed Averostra (Chow and Rozhdestvensky, 1960)
Middle-Late Campanian, Late Cretaceous
Iren Dabasu Formation, Inner Mongolia, China
Material- (AMNH 6376) phalanx II-1 (AMNH online)
(AMNH 6556) metatarsal II (AMNH online)
(AMNH 6744) four caudal vertebrae, 8 distal pedal elements (AMNH online)
(AMNH 6756) metatarsal (AMNH online)
(AMNH 6757) limb fragments, metapodials, phalanx, fragments (AMNH online)
(AMNH 21552) femur
(AMNH 21565) elements
(AMNH 21588)
(AMNH 21774) fibula
(AMNH 21775) pedal phalanx ?II-1
(AMNH 21776) four proximal pedal phalanges
(AMNH 21780) four unguals
(AMNH 21782) manual ungual
(AMNH 21784) four caudal vertebrae
(AMNH 30245) two metatarsal II or IV shafts (AMNH online)
(AMNH 30247) posterior dorsal rib fragment (AMNH online)
(AMNH 30248) proximal anterior rib (AMNH online)
(AMNH 30249) partial coracoid (AMNH online)
(AMNH 30250) distal femur (AMNH online)
(AMNH 30251) proximal femur (AMNH online)
(AMNH 30252) distal femur (AMNH online)
(AMNH 30253) proximal femur (AMNH online)
(AMNH 30254) distal femur (AMNH online)
(AMNH 30255) astragalus (AMNH online)
(AMNH 30256) proximal tibia (AMNH online)
(AMNH 30257) proximal femur (AMNH online)
(AMNH 30258) distal tibia (AMNH online)
(AMNH 30259) proximal metatarsal (AMNH online)
(AMNH 30260) proximal metatarsal (AMNH online)
(AMNH 30298) acetabular fragment (AMNH online)
(AMNH 30299) proximal ischium (AMNH online)
(AMNH 30360) metatarsal III shaft (AMNH online)
(AMNH 80277) distal humerus (AMNH online)
(IVPP or PIN coll.) (small) three partial skeletons (Chow and Rozhdestvensky, 1960)
(IVPP and PIN coll.) <400 specimens (Currie and Eberth, 1993)
Comments- The AMNH specimens listed here are from the online catalogue, which generally lacks identification for ranks between order and family so that Theropoda indet. material is listed as Saurischia.  Yet none of the specimens are likely to be sauropods given Gilmore (1933) never mentioned finding any and to this day only a few elements have been reported (4 in the Erenhot Dinosaur Museum coll., 7 from the Sino-Soviet expedition- Currie and Eberth, 1993; Sonidosaurus).  Most would have been found during the April 22 to May 25 1923 Central Asiatic Expedition, AMNH 6556 on April 30.  The online catalog also specifies AMNH 6756 was discovered in AMNH site 141.  Many of these specimens (AMNH 6556, 30245, 30247-30260, 30298-30299, 30360, 80277) are listed as being from "8 mi. E. of station" which would place them among Third Asiatic Expedition field sites 140-149, with AMNH 6757 listed as 9 miles east, so perhaps site 149.  One exception is AMNH 6744, stated as being found at Elephant Camp (12 miles NW of the station) by de Chardin, who was only on the 1930 expedition.  Based on the elements preserved, specimen numbers and locality of "8 mi. E. of station", sevcral specimens (AMNH 30245, 30247-30260, 30298-30299, 30360) may belong to the two(+?) troodontid individuals noted in the AMNH online catalog represented by specimen numbers AMNH 30261-30297, 30300-30318, 30320-30330 and 30336-30359.
Chow and Rozhdestvensky (1960) noted "three partially complete skeletons of some small carnosaurian dinosaurs" discovered in the June-July 1959 Sino-Soviet expedition, perhaps indicating tyrannosauroids or dromaeosaurids.  Currie and Eberth (1993) stated "A rough tally of Sino-Soviet field identifications shows that ... 'theropods' (including large theropods, small theropods and segnosaurs, but not ornithomimids) were more common (400 specimens)."
References- Gilmore, 1933. On the dinosaurian fauna of the Iren Dabasu Formation. Bulletin American Museum of Natural History. 67, 23-78.
Chow and Rozhdestvensky, 1960. Exploration in Inner Mongolia - A preliminary account of the 1959 field work of the Sino-Soviet Plaeontological Expedition. Vertebrata PalAsiatica. 4(1), 1-10.
Dong, Currie and Russell, 1989. The 1988 field program of The Dinosaur Project. Vertebrata PalAsiatica. 27(3), 233-236.
Dong, 1992. Dinosaurian Faunas of China. China Ocean Press. 188 pp.
Currie and Eberth, 1993. Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People’s Republic of China. Cretaceous Research. 14, 127-144.
Dong, 1993. The field activities of the Sino-Canadian Dinosaur Project in China, 1987-1990. Canadian Journal of Earth Sciences. 30(10), 1997-2001.