Saturday, June 13, 2020

The Unecessary Death of Steneosaurus

Not a dinosaur, but a new paper on the classic crocodylomorph Steneosaurus exemplifies a troubling trend in recent vertebrate taxonomy.  Johnson et al. (2020) reexamine the original material of Steneosaurus, an aquatic croc from the Jurassic of France.  It hadn't been seriously looked at since the 1860s, so this is one of my favorite kinds of paleontology papers- restudying a fragmentary old specimen in a modern light.  What do they find?

We first get a detailed recount of its history, with two decades as Cuvier's "tête à museau plus allongé" (= head with a more elongated snout; I have to praise the authors for translating all the French to English, even in our spoiled era of Google Translate it saves time), before it was named Steneosaurus rostro-major by Geoffroy Saint-Hilaire in 1825.  Eudes Deslongchamps and son tackled it in the 1860s, where they viewed the specimen as too poorly preserved and so "stated that the taxon to represent the genus Steneosaurus should be either ‘Steneosaurus’ megistorhynchus Eudes-Deslongchamps, 1866, or ‘Steneosaurus’ edwardsi Eudes-Deslongchamps, 1868c."  Ha!  You don't get to just take somebody's genus and affix your new species as its type.  They were the last to examine the specimen in detail however, making that a pretty bad note to end on.

Johnson et al. then reexamine the type snout of Steneosaurus, correcting the species name by eliminating the hyphen, officially making it the lectotype, noting Steel had determined the posterior skull to be Metriorhynchus, and illustrating and redescribing the specimen.  Excellent work and very well done.  After eliminating Mycterosuchus nasutus, 'Steneosaurus' leedsi, 'S.' heberti and Lemmysuchus and other machimosaurins based on numerous dissimilar characters, the authors come to the contemporaneous 'Steneosaurus' edwardsi.

"As mentioned before, this was a second species that Eudes-Deslongchamps (1867–69) considered identical to S. rostromajor. These two taxa share a combination of features including:
1. A subcircular, moderately interdigitating premaxilla-maxilla suture.
2. Maxillae ornamented with irregular grooves.
3. A shallower mediolateral compression of the posterior maxillae, as opposed to ‘S.’ heberti (MNHN.F 1890-13).
4. Horizontally flat posterior premaxilla in lateral view.
5. Deep anterior and mid-maxillary reception pits that gradually become shallower towards the posterior maxilla.
6. Subcircular to circular alveoli that remain relatively the same size throughout the maxilla.
7. Teeth with well-pronounced enamel ridges at the base."

Well how cool is that?  They put in the hard work, found the matching more complete specimens, and now we have Steneosaurus edwardsi as a junior synonym of S. rostromajor, giving us a good look at what Steneosaurus really was after two hundred years.

Lectotype of Steneosaurus rostromajor (MNHN.RJN 134c-d) in dorsal (A, B) and ventral (C, D) views. (after Johnson et al., 2020).

But no.

Johnson et al. immediately say "it is important to note that many of these characters may, in fact, be related to sexual dimorphism, ontogeny and intraspecific variation."  True, but that could be said for basically every character supposed to diagnose Mesozoic croc genera, or theropod genera, pterosaur genera, etc..  Unless you have some specific example like 'enamel ridges have been shown to develop with age and both S. rostromajor and S. edwardsi are larger than S? leedsi or S? heberti with weak ridges', then it's just hand-waving.  And no, Johnson et al. never develop such an argument for one of those characters, let alone all seven.

Next, we get "In addition to the sexual dimorphism/ontogeny problem, one of the critical issues about MNHN.RJN 134c-d is that it is poorly preserved."  Sure, but you were still able to perform many comparisons.  Again, the authors never say any of their seven characters are taphonomic, so it's another objection without substance.

Yet the worst rationale for rejecting Steneosaurus is "in reality, the name Steneosaurus is extremely impractical. It was used for many metriorhynchid specimens (e.g. ‘Steneosaurus’ gracilis, ‘Steneosaurus’ palpebrosus and ‘Steneosaurus’ manselii) during much of the 19th century, largely in part due to Cuvier’s metriorhynchid skull region (MNHN. RJN 134a-b) being attributed to the teleosauroid rostral section (MNHN.RJN 134c-d). Indeed, the concise, classical definition of ‘Steneosaurus’ as we interpret it today was not given until the work of both Eudes-Deslongchampses (1868c, 1867–69)"

Substitute Megalosaurus in there to see how ridiculous it is.  That has had over 45 species assigned to it, and was named in the 1820s but didn't have a modern concept associated with it until the 1980s.  When Johnson et al. lament that for Steneosaurus "rather than comparing characters outright, comparison is by process of elimination (or the question of ‘what features does this specimen lack?’)", that perfectly describes the Megalosaurus paralectotype dentary.

"After the Eudes-Deslongchampses’ treatment, what was left was an undiagnostic, chimeric type specimen for S. rostromajor (MNHN.RJN 134) and the genus Steneosaurus was redefined using a new type species that was not accepted by some researchers. In addition, since the Eudes-Deslongchampses, there has been no attempt to rectify this taxonomic nightmare;"

You just showed it was diagnostic, Steel long ago got rid of the chimaeric portion, Eudes-Deslongchamps' stupid attempts to name new type species have no relevance, and you have done the work to finally rectify this taxonomic nightmare.

"Due to these three significant factors (uncertainty of variable characters, poor preservation and
unreasonable name), we have concluded that S. rostromajor, and therefore ‘Steneosaurus’ (MNHN.RJN 134c-d), cannot be confidently assigned to an existing teleosauroid species."

Nope, you just showed it can be assigned to the same species as S. edwardsi.

Actually, I correct myself.  THIS is the worst rationale for rejecting Steneosaurus- "In addition, MNHN.RJN 134c-d was initially diagnosed based on significant orbital and temporal characteristics (from the metriorhynchid MNHN.RJN 134a-b), along with generic rostral ones.  Because the skull material is now known to be from a metriorhynchid, this ‘hybrid type specimen’ factor adds to the doubtful validity of Steneosaurus. According to Article 23.8 of the ICZN Code, ‘a species-group name established for an animal later found to be a hybrid (Art. 17) must not be used as the valid name for either of the parental species (even if it is older than all other available names for them)’ (this also signifies that the species name rostromajor is itself invalid). As such, MNHN.RJN 134c-d serves as an undiagnostic specimen; we, therefore, consider MNHN.RJN 134c-d to be a nomen dubium and, as such, Steneosaurus is treated as an undiagnostic genus."

If the term "parental species" didn't tip you off, Article 23.8 applies to hybrid individuals (those resulting from different species interbreeding), not type specimens chimaerically combined from multiple species.  The Article doesn't even say what Johnson et al. think- it says a name for a hybrid can't be used for either of the species that bred to make it, so that e.g. even if  a mule's scientific name was erected prior to that of horse's or ass's, it can't be the name for horse or ass.  And indeed even the cited Article 17 says that hybrids and chimaeras can be the basis of valid names- "The availability of a name is not affected even if 17.1. it is found that the original description or name-bearing type specimen(s) relates to more than one taxon, or to parts of animals belonging to more than one taxon; or 17.2. it is applied to a taxon known, or later found, to be of hybrid origin..."

If Johnson et al.'s interpretation were right, there goes Gojirasaurus, Protoavis, Chuandongocoelurus, Chilantaisaurus, Fukuiraptor, Coelurus, Alectrosaurus, Dakotaraptor, etc..

Before the big reveal, we have in the Conclusion what can only be described as a lie- "Through character comparison-and-elimination, the only taxon with which MHNH.RJN 134c-d could hypothetically be referred to is ‘S.’ edwardsi, but the two do not share any clear autapomorphic characters or a unique combination of characters."

What are your seven listed characters if not "a unique combination of characters"?  Does any other teleosaurid have them?  If not, they are unique.  In any case, we get the motivation for dumping Steneosaurus twice at the end of the paper-

"We believe that establishing teleosauroid taxonomy from the beginning with a series of ‘clean’ type species/specimens, with every nomenclatural act correctly formulated, is the best course of action, which we will highlight in a forthcoming paper (Johnson, 2019)."

"We believe that establishing teleosauroid taxonomy from the beginning with a series of ‘clean’ type species/specimens, with every nomenclatural act correctly formulated, is the best course of action. This will necessitate a revised teleosauroid taxonomy, in which species previously referred to the genus Steneosaurus are given new generic names. This work will be published by us in a separate contribution, based on the comprehensive teleosauroid phylogenetic analysis in Johnson’s PhD thesis (2019)."

Basically everything I hate about a current trend in vertebrate paleontology- just throw out old specimens and dishonor their authors who correctly reported what was new at the time to come up with your own names.  At least dumping Stegosaurus armatus or designating a neotype for Allosaurus fragilis could be claimed to save time and effort actually analysing the types, if you don't want to do the science to figure out if armatus is actually different from stenops or if fragilis can be distinguished from Saurophaganax.  But Johnson et al. already did all the hard work and found Steneosaurus edwardsi was S. rostromajor, they would just rather use Johnson's new genus name for the taxon.

And their reasons are just grasping at straws.  'Sure we identified these seven charactesrs uniquely shared by Steneosaurus rostromajor and S. edwardsi, but uhh.. could be sexually dimorphic?  Or anything could be individual variation.  Or ontogenetic?  Lots of things turn out to be ontogenetic.  Plus it's broken.  Sooo broken.  Sure we could evaluate characters, but who wants a taxon whose holotype isn't pristine?  Plus a lot of people had stupid ideas about Steneosaurus over the past two hundred years.  What do us scientists do when we have a complicated situation to resolve that was only partially understood historically?  Trash their names and give yourselves credit for new genera.'  Thus Steneosaurus gets the eternal identity of "all evidence points to it being Johnsonosaurus edwardsi, but ehhh... we just sort of ignore it now as Teleosauridae indet. and it's forgotten."

To conclude, Steneosaurus is really outside my wheelhouse.  But if Johnson et al.'s philosophy spreads, we're in danger of losing a lot of historical taxonomy and deserved credit to lazy or selfish authors.  Just look at Microraptor for example, whose holotype of M. zhaoianus lacks a decent skull.  Some decades down the line, what if cranial differences support various Jiufotang species and someone's like 'the postcranial proportions are unique between the M. zhaoianus type and M. hanqingi, but I want a complete type specimen, so Microraptor is an invalid undiagnostic nomen dubium, and instead I propose Mybetterraptorgenus hanqingi and M. gui.'  Just hope they don't pull a Wilson and Upchurch and claim 'Microraptor is invalid and co-ordinate suprageneric Linnean taxa must likewise be abandoned' and replace Microraptorinae with Mybetterraptorgenusinae.

References- Johnson, 2019. The taxonomy, systematics and ecomorphological diversity of Teleosauroidea (Crocodylomorpha, Thalattosuchia), and the evaluation of the genus 'Steneosaurus'. PhD Thesis, University of Edinburgh. 1062 pp.

Johnson, Young and Brusatte, 2020. Emptying the wastebasket: A historical and taxonomic revision of the Jurassic crocodylomorph Steneosaurus. Zoological Journal of the Linnean Society. 189(2), 428-448.

Saturday, May 30, 2020

It's finally January 1, 200n and Phylonyms is published!

Ah the PhyloCode, the so-called future of biological nomenclature whose release has always kept on slipping ever more distantly into the future.  After 20 years of waiting, we now have Phylonyms: A Companion to the PhyloCode, by de Queiroz et al. (2020), "a turning point in the history of phylogenetic nomenclature" according to its introduction.  As the book states "Phylonyms serves as the starting point for phylogenetic nomenclature governed by the PhyloCode. According to the preamble, “This code will take effect on the publication of Phylonyms: A Companion to the PhyloCode, and it is not retroactive.” Thus, names and definitions published here have precedence over any competing names and definitions published either before (or after) the publication of Phylonyms."  So for anyone invested in standardized phylogenetic nomenclature, this is it.  Nothing better is coming down the pipeline in our lifetimes, so let's see what we're stuck with.

First of all, it's expensive.  You can get an ebook for $222 on Amazon or a hardcover sometime after June 9th for $234.  I found an electronic version for $169 plus tax on VitalSource, but you have to use their reader.  It's 1323 pages though, so isn't a bad deal.  That's less than five $37.95 Cretaceous Research pdfs, and I figure this is one of those historical volumes it's good to have, like Sibley and Ahlquist's bird phylogeny book.

The format is an encyclopedia-style list of clades in phylogenetic order with Registration Number, Definition, Etymology, Reference Phylogeny, Composition, Apomorphies, Synonyms, Comments and Literature Cited.  Rather like my Theropod  Database, so no complaints there.  Well, one complaint is really more to do with the PhyloCode itself where they decided to abbreviate definitions with the non-standard del/nabla triangle symbol ∇.  If you want people to start using your format, you might want to choose symbols that exist on a standard keyboard.  Alt+2207 is supposed to generate it in Windows, but results in ƒ here in Blogger.  Anyone know the correct Unicode numbers?

On to the substance, where Phylonyms covers all life.  Dinosaurs are the last section of the book, and non-avian dinosaurs get all of four definitions-



Dinosauria R. Owen 1842 [M. C. Langer, F. E. Novas, J. S. Bittencourt, M. D. Ezcurra, and J. A. Gauthier], converted clade name

Registration Number: 194

Definition: The smallest clade containing Iguanodon bernissartensis Boulenger in Beneden 1881 (Ornithischia/Euornithopoda) Megalosaurus bucklandii Mantell 1827 (Theropoda/Megalosauroidea) and Cetiosaurus oxoniensis Phillips 1871 (Sauropodomorpha).

I'm glad we've standardized which theropod, ornithischian and sauropodomorph are used (or so I thought, see below), but otherwise there's not much to say.  The caveats around which apomorphies are also found in Nyasasaurus and at least some silesaurs illustrate why apomorphy-based definitions are bad.  The reference phylogeny for this and Saurischia is Lloyd et al.'s (2008) supertree, which is quite outdated and has a lot of artifacts from being a supertree.



Saurischia H. G. Seeley 1888 [J. A. Gauthier, M. C. Langer, F. E. Novas, J. Bittencourt, and M. D. Ezcurra], converted clade name

Registration Number: 195

Definition: The largest clade containing Allosaurus fragilis Marsh 1877 (Theropoda/Carnosauria) and Camarasaurus supremus Cope 1877 (Sauropodomorpha), but not Stegosaurus stenops Marsh 1887 (Ornithischia/Stegosauridae).

It's rather odd the same authors didn't choose the same specifiers for each dinosaurian clade as they did in the previous definition, leaving us without a neat node-stem triplet.  Instead they went with the Kischlatian approach of using taxa"mentioned and figured as examples of their respective groups by Seeley (1888)."  This is funny because I don't think this rationale is ever suggested in the PhyloCode, whereas Dinosauria and Saurischia are actually the official examples used for Recommendation 11F encouraging node-stem triplets ("If it is important to establish two names as applying to sister clades regardless of the phylogeny, reciprocal maximum-clade definitions should be used in which the single internal specifier of one is the single external specifier of the other, and vice versa").  Specifically- "If one wishes to define the names Saurischia and Ornithischia such that they will always refer to sister clades, Saurischia might be defined as the largest clade containing Megalosaurus bucklandii Mantell 1827 but not Iguanodon bernissartensis Boulenger in Beneden 1881, and Ornithischia would be defined as the largest clade containing Iguanodon bernissartensis but not Megalosaurus bucklandii. To stabilize the name Dinosauria as referring to the clade comprising Saurischia and Ornithischia, Dinosauria should be defined as the smallest clade containing Megalosaurus bucklandii and Iguanodon bernissartensis." 

Ornithoscelida and its consequences are mentioned, but I'm glad more time is not taken up with it as I expect the hypothesis to fall away as Baron's phylogenetic mistakes are not followed by future authors.



Sauropodomorpha F. R. von Huene 1932 [M. Fabbri, E. Tschopp, B. McPhee, S. Nesbitt, D. Pol, and M. Langer], converted clade name

Registration Number: 295

Definition: The largest clade containing Saltasaurus loricatus Bonaparte and Powell 1980 (Sauropodomorpha) but not Allosaurus fragilis Marsh 1877 (Theropoda) and Iguanodon bernissartensis Boulenger in Beneden 1881 (Ornithischia).

I dislike the use of Saltasaurus as the internal specifier, which is a holdover of Sereno's weird use of deeply nested OTUs when others would be more historically relevant and/or eponymous.  Fabbri et al. defend the choice because "Fossil specimens referred to Saltasaurus loricatus are abundant, the species is well known, and its phylogenetic position is consistent among phylogenetic analyses", but this would be even more true for e.g. Camarasaurus supremus used in Saurischia's definition.  The other specifiers are a mix of those in Dinosauria's and Saurischia's definition, so there's absolutely no consistency.  The reference phylogeny is Otero et al.'s (2015) Sefapanosaurus description using Yates' matrix, so is fine.

There's a rare error in the comments for this entry.  Fabbri et al. state "Segnosaurus galbinensis from the Cretaceous was briefly thought to be a relatively early diverging sauropodomorph (Paul, 1984; Gauthier, 1986; Olshevsky, 1991). More material referable to that species and the discovery of closely related taxa later showed that Segnosaurus galbinensis is part of the Therizinosauria", but material of S. galbinensis besides that initially recovered in the 1970s is not known.



Theropoda O. C. Marsh 1881 [D. Naish, A. Cau, T. R. Holtz, Jr., M. Fabbri, and J. A. Gauthier], converted clade name

Registration Number: 216

Definition: The largest clade containing Allosaurus fragilis Marsh 1877 (Theropoda) but neither Plateosaurus engelhardti Meyer 1837 (Sauropodomorpha) nor Heterodontosaurus tucki Crompton and Charig 1962 (Ornithischia).

Here we've chosen two completely different specifiers for Sauropodomorpha and Ornithischia, so again we have no consistency.  The reference phylogeny is Cau (2018), which is ideal. 



What about the rest?  It's a HUGE volume, and obviously most of Pan-Biota is outside my area of expertise.  One obvious issue is the wildly varying coverage of different clades.  Apparently nobody could be bothered with the vast majority of vertebrates (euteleosts) or animals (insects, except one definition for Trichoptera), and Molluska doesn't even get a definition.  But we do get several entries for edrioasterid taxa down to subfamily-level, generally obscure Paleozoic echinoderms.  Closer to dinosaurs, there's nothing at all for pan-crocs, but we get an entry for Pterosauromorpha for which only Scleromochlus is given as a plausible non-pterosaurian example (perhaps wrongly- Bennett, 2020). 

Then there are the apomorphy-based definitions which will cause headaches in the future.  Look at Apo-Chiroptera- "Definition: The clade for which the unique modifications of the hand, forearm, humerus, scapula, hip, and ankle (see Diagnostic Apomorphies) associated with flapping flight, as inherited by Vespertilio murinus Linnaeus 1758, are apomorphies."  Then you go down to the nine listed sets of Diagnostic Apomorphies like "Modification of the scapula: Scapular spine originates at the posterior edge of the glenoid fossa. Long axis of scapular spine offset 20–30 degrees from axis of rotation of the humeral head. Scapular spine reduced in height—acromion process appears more strongly arched and less well supported than in other mammals. Presence of at least two facets in infraspinous fossa."  These are all going spread out as more stem bats are discovered, and indeed the authors already note "Simmons and Geisler (1998) included the absence of claws on wing digits III-V with this suite of modifications; however, the presence of claws on all the wing digits of Onychonycteris suggests that claws were present primitively in Apo-Chiroptera."

Ungulata is defined by Archibald as "The least inclusive crown clade containing Bos primigenius Bojanus 1827 (= Bos taurus Linnaeus 1758) (Artiodactyla) and Equus ferus Boddaert 1785 (= Equus caballus Linnaeus 1758) (Perissodactyla), provided that this clade does not include Felis silvestris Schreber 1777 (= Felis catus Linnaeus 1758) (Carnivora), Manis pentadactyla Linnaeus 1758 (Pholidota), Vespertilio murinus Linnaeus 1758 (Chiroptera), or Erinaceus europaeus Linnaeus 1758 (Lipotyphla)." But this doesn't exist in molecular studies, including those of ultraconserved elements, which consistently place carnivorans, pangolins and bats closer to perrisodactyls.  So this is likely to be a historical footnote, as well established molecular relationships end up trumping morphological relationships in every example I know of.

Finally, we get Pan-Lepidosauria for the total group of lepidosaurs, which has been Lepidosauromorpha for over thirty years.  Yet Archosauromorpha is retained as "The least inclusive clade containing Gallus (originally Phasianus) gallus (Aves) (Linnaeus 1758), Alligator (originally Crocdilus) mississippiensis (Daudin 1802) (Crocodylia), Mesosuchus browni Watson 1912 (Rhynchosauria), Trilophosaurus buettneri Case 1928 (Trilophosauridae), Prolacerta broomi Parrington 1935 (Prolacertiformes), and Protorosaurus speneri von Meyer 1830 (Protorosauria)" even though Pan-Archosauria is also used for the total group of archosaurs, traditionally the definition of Archosauromorpha.  I agree our new Archosauromorpha deserved a name for being a generally recognized group, whereas whether e.g. choristoderes or sauropterygians fell out closer to lizards or birds is highly unstable.  But I would have rather kept the tradition of -omorpha for the stem clades and gave this a new name.



Overall, I'm not very impressed for something 20 years in the making that intends to be so important.  How do you contradict your own example for choosing specifiers in four papers, where two share the same author list, the other two share another author (Fabbri), and each of those shares an author with both of the first two (Langer and Gauthier)?  And one of those is an editor for the volume.  Nothing could be negotiated in over two decades?  But it's what we have to work with now, and in the name of consistancy I'll adopt the definitions proposed.  Now to see what happens when RegNum goes online.

References- Lloyd, Davis, Pisani, Tarver, Ruta, Sakamoto, Hone, Jennings and Benton, 2008. Dinosaurs and the Cretaceous terrestrial revolution. Proceedings of the Royal Society B. 275, 2483-2490.

Otero, Krupandan, Pol, Chinsamy and Choiniere, 2015. A new basal sauropodiform from South Africa and the phylogenetic relationships of basal sauropodomorphs. Zoological Journal of the Linnean Society. 174, 589-634.

Cau, 2018. The assembly of the avian body plan: A 160-million-year long process. Bollettino della Società Paleontologica Italiana. 57(1), 1-25.

Bennett, 2020. Reassessment of the Triassic archosauriform Scleromochlus taylori: Neither runner nor biped, but hopper. PeerJ. 8:e8418.

de Queiroz, Cantiono and Gauthier, 2020. Phylonyms: A Companion to the PhyloCode, 1st Edition. Taylor & Francis Group. 1323 pp.

Monday, March 16, 2020

What is Oculudentavis if it's not a theropod?

In my last post, I argued the recently described Oculudentavis (Xing et al., 2020) is not a theropod.  So what is it?  To answer that question, I entered it into Simoes et al.'s (2018) sauropsid analysis which emphasizes basal lepidosauromorphs and comes out with basal gekkos and nested iguanians even using just morphological characters.  To test Jingmai's avialan hypothesis, I also added Archaeopteryx to the matrix.  The result is 384 MPTs of 2337 steps each.

Strict consensus of 384 MPTs of Simoes et al.'s (2018) analysis after adding Oculudentavis and Archaeopteryx.  Compare to Extended Data Figure 3 of Simoes et al..
As you can see, Oculudentavis resolves as a stem-squamate in a trichotomy with Huehuecuetzpalli and squamates, while Archaeopteryx is an archosauromorph sister to Erythrosuchus.  And this matrix didn't score for scleral ossicle shape, posttemporal fenestra size or maxillary tooth row length.  After scoring Oculudentavis, its teeth are clearly not acrodont, it seems to have a ventral parietal fossa and  lacks an ossified laterosphenoid.  The authors could have made it easier to evaluate by separating the cranial elements in the 3D pdf file.  As it is, a lot of palatal and braincase info is uncertain.  But Huehuecuetzpalli is Albian compared to Oculudentavis' Cenomanian, and has a skull length of 32 mm (19 mm in the juvenile) versus 14 mm in Oculudentavis.


Huehuecuetzpalli skull (top; after Reynoso, 1998), Oculudentavis skull and separate mandible (middle; after Xing et al., 2020), and Archaeopteryx skull (after Rauhut, 2014).

References- Reynoso, 1998. Huehuecuetzpalli mixtecus gen. et sp. nov: A basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodriguez, central Mexico.  Philosophical Transactions of the Royal Society B: Biological Sciences. 353, 477-500.
Rauhut, 2014. New observations on the skull of Archaeopteryx. Paläontologische Zeitschrift. 88(2), 211-221.

Simōes, Caldwell, Talanda, Bernardi, Palci, Vernygora, Bernardini, Mancini and Nydam, 2018. The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps. Nature. 557(7707), 706-709.



Xing, O'Connor, Schmitz, Chiappe, McKellar, Yi and Li, 2020. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579, 245-249.

Thursday, March 12, 2020

Oculudentavis is not a theropod

Hi all.  This week we got the announcement of a tiny theropod skull in Myanmar amber, which was bound to happen eventually as amazing finds from that deposit keep being published.  Alas, whatever Oculudentavis is, it's not a theropod.

Oculudentavis skull (after Xing et al., 2020).

Just look at it.  No antorbital fenestra, incomplete ventral bar to the laterotemporal fenestra, huge posttemporal fenestrae, teeth that extend posteriorly far under the orbit...

All of which might be coincidental, but then look at the mandible.

Oculudentavis mandible (after Xing et al., 2020).

That spike-like coronoid process is classic lepidosaur, plus the dentary is way too long compared to the post-dentary elements, then the description says "The tooth geometry appears to be acrodont to pleurodont; no grooves or sockets are discernable."  And of course "the scleral ring is very large and is formed by elongated spoon-shaped ossicles; a morphology similar to this is otherwise known only in lizards (for example, Lacerta viridis)."

Add to this the size of this partially fused specimen being smaller than any extant bird (14 mm), and no feather remains, and why is this a theropod again?  The endocast is big, but why not a clade of brainier lizards or late surviving megalancosaurs by the Cenomanian?

The authors add it to Jingmai's bird analysis where it ends in a huge polytomy closer to Aves than Archaeopteryx, but outside fake Ornithuromorpha.  That's often what happens when a taxon is wrongly placed in a clade.  Note the figured placement between Archaeopteryx and Jeholornis is only found using implied weights.  At least add it to e.g. Nesbitt's or Ezcurra's archosauromorph analyses, or Cau's theropod analyses before assuming it's a bird.

Thanks to Ruben Molina Perez for suggesting this issue in the first place.

Reference- Xing, O'Connor, Schmitz, Chiappe, McKellar, Yi and Li, 2020. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature. 579, 245-249.

Monday, January 20, 2020

Details on Teinurosaurus and random musings

Hi all.  When updating The Theropod Database I noticed my entry for Teinurosaurus is pathetically bad- wrong authors, wrong age, wrong size, and generally missing the complicated history of this innocuous vertebra.  How embarrassing!  So here's the revised version that will be uploaded-

Teinurosaurus Nopcsa, 1928
= Saurornithoides Nopcsa, 1928 (preoccupied Osborn, 1924)
= Caudocoelus Huene, 1932
T. sauvagei (Huene, 1932) Olshevsky, 1978
= Caudocoelus sauvagei Huene, 1932
Tithonian, Late Jurassic
Mont-Lambert Formation, Hauts-de-France, France

Holotype- (BHN2R 240; = Boulogne Museum 500) incomplete distal caudal vertebra (75 mm)
Diagnosis- Provisionally indeterminate relative to Kaijiangosaurus, Tanycolagreus and Ornitholestes.
Other diagnoses- (after Huene, 1932; compared to Elaphrosaurus) centrum wider; narrower ventral surface; ventral median groove wider; transversely narrower prezygapophyses.
While Huene attmpted to distinguish Teinurosaurus from Elaphrosaurus, only the wider median ventral groove is apparent in existing photos of the former.  This is compared to the one distal caudal of the latter figured in ventral view, but as Kobayashi reports grooves become distally narrower in Harpymimus while Ostrom reports they become distally wider in Deinonychus, groove width is not considered taxonomically distinctive at our current level of understanding.  Indeed, this lack of data is most relevent to both diagnosing and identifying Teinurosaurus.  Very few taxa have detailed descriptions of distal caudal vertebrae or more than lateral views figured, let alone indications of variation within the distal caudal series.  So the facts that Fukuiraptor and Deinonychus share ventrally concave central articulations with Teinurosaurus in their single anteriorly/posteriorly figured distal caudal vertebra, or that Afromimus, "Grusimimus" and Falcarius also have have wide ventral grooves in their few ventrally figured distal caudals, are not considered taxonomically important. 
Comments- Sauvage (1897-1898; in a section written in January 1898) first mentioned a distal caudal vertebra he referred to the ornithischian Iguanodon prestwichii (now recognized as the basal styracosternan Cumnoria prestwichii) - "We are disposed to regard as belonging to the same species the caudal vertebra of a remote region, the part which we figure under n ° 7, 8" [translated].  Note Galton (1982) was incorrect in claiming Sauvage reported on this specimen in his 1897 paper (written December 6), which includes a section on prestwichii nearly identical to the 1897-1898 one but which lacks the paragraph describing this vertebra.  This could provide a specific date of December 1897 to January 1898 for the discovery and/or recognition of the specimen.  Huene (1932) correctly noted Sauvage mislabeled plate VII figure 8 as dorsal view, when it is in ventral view as understood by the text.  Compared to Cumnoria, the caudal is more elongate (length 3.93 times posterior height compared to 2.54 times at most), has a ventral median groove instead of a keel, and the prezygapophyseal base in 71% of the anterior central height compared to ~30-40%, all typical of avepods.  Nopcsa (1928) recognized its theropod nature and in his list of reptile genera meant to use a footnote to propose Teinurosaurus as a "new name for the piece described and figured by Sauvage (Direct. Traveaux Geol. Portugal Lisbonne 1897-1898, plate VII, Fig. 7-10) as late caudal of Iguanodon Prestwichi."  Teinurosaurus is listed as an aublysodontine megalosaurid (not as an ornithomimine, contra Galton), roughly equivalent to modern Eutyrannosauria.  However due to a typographical error, the footnote's superscript 1 was placed after Saurornithoides instead of Teinurosaurus.  Sauvage (1929) corrected this in an addendum- "footnote 1 does not refer to Saurornithoides (line 19 from below) but to Teinurosaurus (last line of text)."  Unfortunately, Huene missed the addendum, and thus wrote "Nopcsa recognized in 1927 (43, p. 183) that this was a coelurosaur and intended to give it a name, but used one already used by Osborn, namely "Saurornithoides" (91, 1924, p. 3- 7). For this reason, a new name had to be given here" [translated].  Huene's proposed new name was Caudocoelus sauvagei, placed in Coeluridae and "somewhat reminiscent of Elaphrosaurus."  Huene is also perhaps the first of several authors to place the specimen in the Kimmeridgian, when it is actually from the Tithonian (Buffetaut and Martin, 1993; as Portlandian).  Galton wrote "Lapparent and Lavocat (1955: 801) gave a line drawing of the vertebra after Sauavage (1898) and included it in the section on Elaphrosaurus" and that the specimen "was referred to Elaphrosaurus by Lapparent and Lavocat (1955)."  This was perhaps done because Huene explicitly compared the two, ironically making it the only taxon distinguished from Teinurosaurus at the time.  Most of Huene's characters cannot be checked in the few published photos of Teinurosaurus, but the ventral median sulcus is indeed much wider than Elaphrosaurus.  Ostrom (1969) was the first author to detail Nopcsa's (1929) addendum, stating "Nopcsa's name Teinurosaurus has clear piority over Huene's Caudocoelus, but since Nopcsa failed to provbide a specific name, Teinurosaurus is not valid."  Olshevsky (1978) solved this by writing "Teinurosaurus has clear priority over Caudocoelus, as noted in Ostrom 1969, and it is certainly a valid generic name. The species Caudocoelus sauvagei is proposed here as the type species of the genus Teinurosaurus, resulting in the new combination Teinurosaurus sauvagei (von Huene 1932) as the proper name of the type specimen."  He also claimed "the specimen itself, unfortunately, was destroyed during World War II and thus must remain a nomen dubium."  This was repeated by Galton, but as Buffetaut et al. (1991) wrote- "Contrary to a widespread opinion (expressed, for instance, by Lapparent, 1967), the vertebra in question has survived two world wars and years of neglect, like a large part of the other fossil reptile remains in the collections of the Boulogne Natural History Museum (see Vadet and Rose, 1986)."  Olshevsky noted Steel misunderstood Nopsca in a different way, believing Teinurosaurus instead of Aublysodon was a "name, proposed by Cope in 1869 ... used instead of Deinodon", as stated under superscript 2.  Galton did have the first modern opinion on Teinurosaurus' affinities, stating "In addition to Elaphrosaurus, elongate prezygapophyses occur in the allosaurid Allosaurus and the dromaeosaurid Deinonychus, so this caudal vertebra can only be identified as theropod, family incertae sedis."  Buffetaut and Martin (1993) agreed, saying "no really distinctive characters that would allow a familial assignment can be observed."  Ford (2005 online) gave the type repository as "Dortigen Museum", but this is a misunderstanding based on Huene's "Boulogne-sur-mer (Nr. 500 im dortigen Museum)", which translated is "Boulogne-sur-mer (No. 500 in the museum there)", referring to the Boulogne Museum where it has always been held.  It was originally number 500, but was recatalogued at some point.
Sauvage lists the vertebra's length as 75 mm and his plate at natural size would have it be 79 mm, Huene lists it as 11 cm (110 mm) and his figure at 1:2 size would have it be 152 mm.  Galton's drawing with supposed 5 cm  scale would have it be 235 mm, while Buffetaut and Martin's plate with scale would leave it at 74 mm.  As Huene's and Galton's figures are taken from Sauvage's original plate and the newest and unique photo matches Sauvage's reported length almost exactly, 75 mm is taken as the correct length.
Relationships- While prior authors haven't specified Teinurosaurus' relationships past Theropoda (besides Lapparent and Lavocat's apparent synonymy with Elaphrosaurus), there are several ways to narrow down its identity.  Only neotheropods are known from the Late Jurassic onward, so coelophysoid-grade taxa are excluded.  Some theropod clades were too small to have a 75 mm caudal, including most non-tyrannosauroid coelurosaurs besides ornithomimosaurs, therizinosaurs and eudromaeosaurs.  The former two are unknown from the Jurassic, and additionally paravians like eudromaeosaurs lack any neural spine by the time the centrum gets as elongate as Teinurosaurus (e.g. by caudal 12 in Deinonychus at elongation index of 2.4).  Teinurosaurus has an elongation index (centrum length/height) of 3.9, which also excludes Ceratosauridae, Beipiaosaurus + therizinosauroids and oviraptorosaurs.  Prezygapophyses basal depth is significantly less in ceratosaurids, megalosaurids, carnosaurs except Neovenator, compsognathids, Fukuivenator and Falcarius.  Remaining taxa are elaphrosaur-grade ceratosaurs, piatnitzkysaurids, Neovenator and basal tyrannosauroids. 
References- Sauvage, 1897. Notes sur les Reptiles Fossiles (1).  Bulletin de la Société géologique de France. 3(25), 864-875.
Sauvage, 1897-1898. Vertebres Fossiles du Portugual, Contributions a l'etude des poissions et des reptiles du Jurassique et du Cretaceous. Direction des Travaux Geologiques Portugal. 1-46.
Osborn, 1924. Three new Theropoda, Protoceratops zone, central Mongolia. American Museum Novitates. 144, 1-12.
Nopcsa, 1928. The genera of reptiles. Palaeobiologica. 1, 163-188.
Nopcsa, 1929. Addendum "The genera of reptiles". Palaeobiologica. 2, 201.
Huene, 1932. Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte. Monographien zur Geologie und Palaeontologie. 4(1), 361 pp.
Lapparent and Lavocat, 1955. Dinosauriens. In Piveteau (ed.). Traite de Paleontologie. Masson et Cie. 5, 785-962.
Lapparent, 1967. Les dinosaures de France. Sciences. 51, 4-19.
Ostrom, 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum of Natural History Bulletin. 30, 1-165.
Steel, 1970. Part 14. Saurischia. Handbuch der Paläoherpetologie/Encyclopedia of Paleoherpetology. Gustav Fischer Verlag. 87 pp.
Olshevsky, 1978. The archosaurian taxa (excluding the Crocodylia). Mesozoic Meanderings. 1, 50 pp.
Galton, 1982. Elaphrosaurus, an ornithomimid dinosaur from the Upper Jurassic of North America and Africa. Paläontologische Zeitschrift. 56, 265-275.
Vadet and Rose, 1986. Catalogue commente des types et figures de dinosauriens, ichthyosauriens, sauropterygiens, pterosauriens et cheloninens du Musée d'Histoire Naturelle de Boulogne-sur-Mer. In E. Buffetaut, Rose and Vadet (eds.). Vértébrés Fossiles du Boulonnais. Mémoires de la Société Académique du Boulonnais. 1(2), 85-97.
Rose, 1987. Redecouverte d'une vertebre caudale reptilienne (Archosauriens) de status controverse et provenant des terrains jurassiques superieurs du Boulonnais. Bulletin de la Société académique du Boulonnais. 1(5), 150-153.
Buffetaut, Cuny and le Loeuff, 1991. French Dinosaurs: The best record in Europe? Modern Geology. 16(1-2), 17-42.
Buffetaut and Martin, 1993. Late Jurassic dinosaurs from the Boulonnais (northern France): A review. Revue de Paléobiologie. 7(vol. spéc.), 17-28.
Ford, 2005 online. http://www.paleofile.com/Dinosaurs/Theropods/Teinurosaurus.asp

* minor edits (see Marjanovic's comment)

And before we go, here are a couple more tidbits I've noticed in the upcoming update...

- That theropod tail preserved in Burmese amber (DIP-V-15103) described by Xing et al. (2016) was only placed as specifically as a non-pygostylian maniraptoriform.  But as the deposits are Gondwanan (e.g. Poinar, 2018), the range of potential Cenomanian theropods is better understood.  And only one group has caudal centra over three times longer than tall- unenlagiines.  I bet DIP-V-15103 is our first sample of preserved plumage in an unenlagiine, which makes you wonder if the weird alternating barb placement was a feature that evolved on Gondwana, and if so did Rahonavis' remiges exhibit it too?

- Does anyone realize both "Tralkasaurus" (Cerroni et al., 2019) and "Thanos" (Delcourt and Iori, 2018) are nomina nuda?  Neither are in an  official volume yet, though "Tralkasaurus" is scheduled for March and "Thanos" will probably make it this year if the average papers per volume of Historical Biology holds up.  "Tralkasaurus" has an empty space in its "Zoobank registration:" section, while the "Thanos" paper doesn't mention ZooBank at all, and neither  show up in ZooBank searches.  Also, one of "Thanos"' supposed autapomorphies is a deep prezygapophyseal spinodiapophyseal fossa, which does not exist in abelisaurs as it would require a spinodiapophyseal lamina.  The labeled structure seems internal, probably the centroprezygapophyseal fossa or prezygapophyseal centrodiapophyseal fossa based on CT-scanned noasaurid cervical DGM929-R.  That leaves axial pleurocoel size and distance from each other, and ventral keel strength as suggested characters.  Which can only be compared to Carnotaurus among brachyrostrans.  Hmmm...

References- Xing, McKellar, Xu, Li, Bai, Persons IV, Miyashita, Benton, Zhang, Wolfe, Yi, Tseng, Ran and Currie, 2016. A feathered dinosaur tail with primitive plumage trapped in Mid-Cretaceous amber. Current Biology. 26(24), 3352-3360.

Delcourt and Iori, 2018. A new Abelisauridae (Dinosauria: Theropoda) from São José do Rio Preto Formation, Upper Cretaceous of Brazil and comments on the Bauru Group fauna. Historical Biology. DOI: 10.1080/08912963.2018.1546700

Poinar, 2018. Burmese amber: Evidence of Gondwanan origin and Cretaceous dispersion. Historical Biology. DOI: 10.1080/08912963.2018.1446531


Cerroni, Motta, Agnolín, Aranciaga Rolando, Brissón Egli and Novas, 2019. A new abelisaurid from the Huincul Formation (Cenomanian-Turonian; Upper Cretaceous) of Río Negro province, Argentina. Journal of South American Earth Sciences. 98, 102445.

Thursday, January 2, 2020

Happy New Year 2020

Hi all.  A Theropod Database update is online, with the main additions being troodontid information and info from the Hayashibara Museum of Natural Sciences Research Bulletins 1-3.  I love these publications and wish more like them existed for other collections.  They detail the expeditions into Mongolia with exact discovery dates and field numbers for taxa like Nomingia, Elsornis and Aepyornithomimus, and tons of still undescribed specimens.  It's amazing just how many ornithomimosaurs are known from the Bayanshiree Formation for instance, when only the Garudimimus holotype has been described.  There are over twenty more including the sort-of-described "Gallimimus" "mongoliensis" specimen IGM 100/14.  So often for new taxa, especially those from the Jehol biota, no information is provided in the description as to when the specimen was discovered.  I get that many are found by non-professionals and given to museums, but at least say "the specimen was given to the museum on x-x-xx by someone who said it was excavated around year y."  Next up, halszkaraptorine and dromaeosaurid updates...

undescribed ?Gobivenator skull (HMNS coll.; field number 940801 TS-I WTB) (after Tsogtbaatar and Chinzorig, 2010).
Reference- Tsogtbaatar and Chinzorig, 2010. Fossil specimens prepared in Mongolian Paleontological Center: 2002–2008. Hayashibara Museum of Natural Sciences Research Bulletin. 3, 155-166.

Thursday, August 22, 2019

Therizinosaurs in the Lori matrix

Next up are therizinosaurs.  These are one of the best analyzed clades because I incorporated all of Zanno's (2010) characters, which is by far the largest and most recent analysis of the group until the Lori paper was published.  The topology is-


Falcarius is the most basal taxon shown of course, but Martharaptor was pruned a posteriori and can fall out anywhere in Therizinosauria outside the Alxasaurus plus Segnosaurus clade.  I tried including Thecocoelurus, but the Lori matrix is pretty terrible when it comes to scoring single vertebrae-

Thecocoelurus                       ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ???????(01)0? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ???1?????? ?????????? ?????2???? ?????????? ?????????? ?????????? ?????????? ???????0?? ?????????? ?????????? ?????????? ?????1???? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ??0??????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ??????????

Jianchangosaurus fell out in the same place as its original description, with Cau's (2018) placement in Alvarezsauroidea taking 18 more steps so is very unlikely.  Mine is the only published matrix besides Senter (2011) and its derivatives to use information from the second Beipaiosaurus specimen, and incorporated photos from Zanno and the new paper on the holotype skull elements too.

Beipiaosaurus inexpectus holotype (IVPP V11559) cervical vertebra in dorsal view (courtesy of Zanno).
Zanno also provided photos of Alxasaurus and Enigmosaurus, and its depressing how much of the former is lost.  Enigmosaurus rather famously was shown by Zanno to not resemble Barsbold's original illustration that was the only reference picture known for over two decades.  Placing Enigmosaurus closer to Segnosaurus than Neimongosaurus or Erliansaurus as in Zanno's tree takes 4 more steps.  Forcing Enigmosaurus and Erlikosaurus to be sister taxa to simulate the synonymy mentioned by Barsbold (1983) takes 4 steps, so seems unlikely.  The duo moves between Nanshiungosaurus and the Segnosaurus plus Nothronychus clade.  We were the first analysis to include "Chilantaisaurus" zheziangensis, which emerged in a polytomy with Alxasaurus, Enigmosaurus and therizinosaurids.

Alxasaurus elesitaiensis holotype (IVPP V88402a) chevrons in right lateral view (natural order reversed) (courtesy of Zanno).
As was the case with Archaeornithomimus? bissektensis, we didn't include the possible chimaera of Bissekty Therizinosauria as an OTU, unlike Sues and Averianov (2015).  But if you do want to experiment with it, here's the scorings.  It emerges in a polytomy in the Suzhousaurus plus Therizinosaurus clade of therizinosaurids.  Btw, Archaeornithomimus? bissektensis does fall out most parsimoniously sister to A. asiaticus when all Bissekty material is used.

'Bissekty-Therizinosauroidea'       ????1??0?? ????1????? ?????1???? ?1???????? ?????{01}1000 ?01??????? 00???????? 2??21?0??? ???????00{123} {12}00(01)2011?? ??0???0(01)00 ??11????{12}? ?{01}0?100??? ?????????? ?1{01}?0????? ??0?0???{012}0 000(01)?010?? ?????????? ?????????? ?????0{12}?00 1?0???0??0 ??0??{01}0??? 0?1??????? ????0?1?0? {01}0?1???{01}?? ??0??????? ?????????? ?????????0 ???001??00 ??00?01?1? 10???????? ?????????1 ???0?????? ???1?????? ??????0??1 0???1(12)???? ????0???1? ????0?011? ???0????0? ???0{12}0???? ????????0? 0?0????1?? ?????????? ??010101?1 ??0?0(01)???? ?????{01}010? ???100???? ????????11 1010?????? ??0??0???? ?????????? ?????????? ??????0??? ??00?????? ?00??????? ?????????? ???????0-- -??00??010 ?????????? ??????-??? ???-010??1 0100????00 10?1?00??? ???0?00??? ?????????? ????0????? ???000???? ?0???-???? ?????????? ?????001??

Enigmosaurus mongoliensis holotype (IGM 100/84) synsacrum and ilium in ventral view (courtesy of Zanno).
Next is Therizinosauridae itself, which we refined Zhang et al.'s (2001) definition of to include type species.  Therizinosaurids first split into a clade of Erliansaurus, Neimongosaurus, Suzhousaurus and Therizinosaurus.  Forcing the former two to be outside a clade of Suzhousaurus, Therizinosaurus and the taxa below, as in Zanno's tree, takes 5 more steps.  Notably, we did not include the hindlimb IGM 100/45 in the Therizinosaurus OTU since there's no overlap and its not even particularly large.  But here's the Therizinosaurus OTU including the hindlimb.  Using this version of Therizinosaurus leaves the tree basically the same but destabilizes it somewhat in that Therizinosaurus and Erlikosaurus can now go in multiple positions within Therizinosauridae, and the Nanchao embryos are in a trichotomy with the Suzhousaurus clade and the Nothronychus clade.  Is this an indication the hindlimb produces homoplasy and so might not belong to Therizinosaurus?

Therizinosaurus                     ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ????????01 0110021000 01?0001100 00001110?? ?????????? ?????????? ?????????? ???0???010 1?0000000? 0?1??1???? ?????????? ?????????? 000??0???? ??????3??1 ?????????0 ???00????? 0?1?0?1??? ?????0???? ?????????1 ?????????? ?????0???? ?????????? ?????????? 1011010101 100100??1? ????{12}?00?? 00?12110?? 101??????? 0????0?111 00?010???? ????????1? ?????????? ????100111 1101110??? ?????????? ????????1? ?1???????? ?????????1 ???0?????? ?000?????? ?????0???1 ?????????? ?????????? ?????????? ?????????? ?????0???? ??????-00? ?00-000001 0?0100??0? 10000???0{01} ?{01}?0000??0 {01}0???????? ????????00 ?00?????0- -??11-???? ?????????? ???1?0???0
Segnosaurus galbinensis paratype (IGM 100/83) cervical neural arch in right lateral view (courtesy of Zanno).
Now comes the Nanchao therizinosaur embryos, those described by Kundrat et al. inside dendroolithid eggs.  While including such young specimens might be seen as risky, my ontogenetically conservative scoring method with state N seems to have worked fine here.  They fall out where you'd expect a Santonian-Campanian therizinosaur to do so.  Following that is Nanshiungosaurus brevispinus, which Senter et al. (2012) recovered as the next most derived therizinosaur after Alxasaurus.  Forcing it into this basal position takes 4 steps.  Nanshiungosaurus? bohlini was included but pruned a posteriori since it can go anywhere in the Segnosaurus plus Nothronychus clade.  Forcing Nanshiungosaurus monophyly is just a single step longer though, while forcing bohlini to be sister to the contemporaneous Suzhousaurus takes 2 steps.

Segnosaurus itself (which Zanno also provided photos of) pairs with ex-Alectrosaurus forelimb AMNH 6368, which has only previously been analyzed by Zanno (2006) where it pairs with Erliansaurus.  Forcing that here compared to other taxa she included results in trees 3 steps longer.  Erlikosaurus groups with the Nothronychus species in a trichotomy where it can be sister to either species.  Forcing Nothronychus monophyly takes only a single step, but note that no proposed Nothronychus characters involve elements that can be compared to Erlikosaurus (humerus and pes).  Forcing Erlikosaurus to group with Therizinosaurus as in Senter et al. requires only a single step, with Erlikosaurus moving to the Therizinosaurus clade.

Next time, oviraptorosaurs...

References-  Barsbold, 1983. Carnivorous dinosaurs from the Cretaceous of Mongolia. Transactions of the Joint Soviet-Mongolian Palaeontological Expedition. 19, 117 pp.

Zhang, Xu, Sereno, Kwang and Tan, 2001. A long-necked therizinosauroid dinosaur from the Upper Cretaceous Iren Dabasu Formation of Nei Mongol, People’s Republic of China. Vertebrata PalAsiatica. 39(4), 282-290.

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.

Senter, 2011. Using creation science to demonstrate evolution 2: Morphological continuity within Dinosauria. Journal of Evolutionary Biology. 24(10), 2197-2216.


Senter, Kirkland, DeBlieux, Madsen and Toth, 2012. New dromaeosaurids (Dinosauria: Theropoda) from the Lower Cretaceous of Utah, and the evolution of the dromaeosaurid tail. PLoS ONE. 7(5), e36790.

Sues and Averianov, 2015. Therizinosauroidea (Dinosauria: Theropoda) from the Upper Cretaceous of Uzbekistan. Cretaceous Research. 59, 155-178.

Cau, 2018. The assembly of the avian body plan: A 160-million-year long process. Bollettino della Società Paleontologica Italiana. 57(1), 1-25.

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. DOI: 10.7717/peerj.7247