Wednesday, December 31, 2014

Neotyping past a diagnostic syntype - Majungasaurus edition

One of my pet peeves is the recent trend to petition the ICZN to designate a more complete specimen the neotype of a taxon when the fragmentary holotype hasn't even been shown to be undiagnostic.  A recent example is Paul and Carpenter's (2010) Allosaurus petition when the holotype hasn't even been well described outside a thesis or ever compared to the other accepted allosaurid genus (Saurophaganax).  Generally thoughts about which specimens are diagnostic varies, so regardless of how much laziness is involved in these petitions, there's excusable subjectivity too.  But while researching Allosaurus' case for the big New Years Theropod Database update, I found a Majungasaurus petition I hadn't heard about, and it's a weird one.

The applicable ICZN Article is 75.5- "When an author considers that the taxonomic identity of a nominal species-group taxon cannot be determined from its existing name-bearing type (i.e. its name is a nomen dubium), and stability or universality are threatened thereby, the author may request the Commission to set aside under its plenary power [Art. 81] the existing name-bearing type and designate a neotype."

Most of the original syntypes of Megalosaurus crenatissimus- A. Fourth premaxillary tooth FSL 92.306b (left) and posterior dentary tooth FSL 92.306a (right) in lateral view. B. Pedal ungual FSL 92.290 in side view. C. Distal caudal vertebra FSL 92.289 in lateral view. D. sacral centrum FSL 92.343 in lateral view. Scale equals 10 mm for A, and 30 mm for B-D.  After Krause et al., 2007.
A brief history of Megalosaurus/Majungasaurus crenatissimus is as follows.  Deperet (1896) described crenatissimus based on five unassociated elements- two teeth, two partial vertebrae, and a partial pedal ungual.  Lavocat (1955) later described a dentary he referred to crenatissimus, based on dental similarity.  More complete skulls and skeletons were described in the 90s and 00s.  Krause et al. (2007) tried to make the dentary the type specimen, but this can't be done without an ICZN petition, as I said at the time.  So they did the right thing in a way, and petitioned the ICZN (Carrano et al., 2009).

Neotype of Majungasaurus crenatissimus, dentary MNHN.MAJ 1 in A. lateral, B. dorsal, and C. medial views.  Scale equals 30 mm. After Krause et al., 2007.
The problem here is that for Article 75.5 to work, the type must be a nomen dubium.  Carrano et al. state "As several authors have confirmed (Sampson et al., 1996, 1998; Krause et al., 2007), the original Depret type specimens are indeed indeterminate as to genus and species, although they can be identified as belonging to the family ABELISAURIDAE. Thus the taxonomic identity of the species Megalosaurus crenatissimus as a nominal species-group taxon cannot be determined from the existing name-bearing type materials."  Sampson et al. (1996) never says this, and indeed refers a premaxilla to crenatissimus based on similarity to Deperet's syntype teeth.  Sampson et al. (1998) did support this position (merely via the statement "none of the specimens appear to be diagnostic to the generic level" that was not supported by any data), which is why they called the new more complete specimens Majungatholus atopus, a name based on a skull roof described in the 70s.

Most importantly though, Krause et al. (2007) say the opposite of what Carrano et al. claim they did.  Krause et al. state "Furthermore, detailed examination of the teeth preserved in MNHN.MAJ 1 [the dentary] by Smith (this volume) reveals that they fall within the same size and shape parameters as the two isolated teeth (FSL 92.306a-b) described by Depéret (1896a, b), those preserved in the gnathic elements of adult individuals described by Sampson and Witmer (this volume; e.g., FMNH PR 2008, 2100; UA 8709, 8716, and 8717), and the thousands of isolated teeth recovered from the Maevarano Formation by Mahajanga Basin Project personnel and others. The teeth of the Malagasy abelisaurid most closely resemble those of AMNH 1753, 1955, and 1960 from the Late Cretaceous of India (referred to Indosuchus raptorius by Chatterjee, 1978) but, importantly, the Malagasy taxon possesses weakly developed interdenticular sulci whereas the Indian specimens lack them (Smith, this volume)."

If we go to Smith's paper in Sampson and Krause's edited volume, we read- "The morphology of FSL 92.306a is basically as Depéret (1896) described it (Krause et al., this volume:fig. 4A), except that the distal curvature profile is less strongly curved. Overall, the crown is very similar in morphology to the distal dentary teeth of Majungasaurus discovered subsequently (Fig. 21). The DFA classified FSL 92.306a as Majungasaurus (26.74 D2, p .001; Table 2), supporting the hypothesis that the tooth is morphologically congruent with dental material of this animal. I am thus confident in referring this crown to Majungasaurus."

So the authors of the petition claim their own work supports Deperet's syntypes as undiagnostic, but their own cited work actually says the reverse- that one of Deperet's teeth is identical to those in more complete specimens AND that these Malagasy teeth can be distinguished from the most similar taxon.  Now we can argue about whether the tooth actually is diagnostic, but I think the more important issue here is that Carrano et al. seem to have misrepresented the conclusions of their own work as evidence in their petition.  Even if they changed their minds between 2007 and 2009, it would still be wrong to cite their older work for supporting a position it didn't.  So of course given the lack of Comments, the Commission would assume Carrano et al. are citing their own work correctly and pass the motion, as they think the work has verified Deperet's syntypes are undiagnostic, thus fulfilling Article 75.5.  And that's what they did, declaring the dentary to be the neotype in 2011.  But if they knew the cited work actually argued a syntype tooth was diagnostic, they might not have.  Though I can't recall a petition being rejected, so who knows.

It's history now, and the dentary will be the neotype unless another is petitioned into existence in the future, but what should have happened is for Krause et al. to make FSL 92.306a the lectotype of crenatissimus without the need of the ICZN, then if later studies found another taxon with identical teeth, the ICZN could be petitioned for a neotype.  Ah well, dentary it is.

References- Deperet, 1896. Note on the sauropod and theropod dinosaurs from the Upper Cretaceous of Madagascar. Bulletin de la Societe Geologique de France, 3rd series. 24, 176.

Lavocat, 1955. Sur une portion de mandibule de Théropode provenant du Crétacé supérieur de Madagascar. Bulletin du Muséum National d’Histoire Naturelle à Paris. 27, 256-259.

Sampson, Krause, Dodson and Forster, 1996. The premaxilla of Majungasaurus (Dinosauria: Theropoda) with implications for Gondwanan Paleobiography. Journal of Vertebrate Paleontology. 16(4), 601-605.

Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998. Predatory dinosaur remains from Madagascar: Implications for the Cretaceous biogeography of Gondwana. Science, 280, 1048-1051.

Krause, Sampson, Carrano and O'Connor, 2007. Overview of the history of discovery, taxonomy, phylogeny, and biogeography of Majungasaurus crenatissumus (Theropoda: Abelisauridae) form the Late Cretaceous of Madagascar. In Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8, 1-20.

Smith, 2007. Dental morphology and variation in Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. In Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8, 103-126.

Carrano, Krause, O'Connor and Sampson, 2009. Case 3487 Megalosaurus crenatissimus Depéret, 1896 (currently Majungasaurus crenatissimus; Dinosauria, Theropoda): Proposed replacement of the holotype by a neotype. Bulletin of Zoological Nomenclature. 66(3), 261-264.

Paul and Carpenter, 2010. Allosaurus Marsh, 1877 (Dinosauria, Theropoda): Proposed conservation of usage by designation of a neotype for its type species Allosaurus fragilis Marsh, 1877. Bulletin of Zoological Nomenclature. 67(1), 53-56.

ICZN, 2011. Opinion 2269 (Case 3487) Megalosaurus crenatissimus Depéret, 1896 (currently Majungasaurus crenatissimus; Dinosauria, Theropoda): Designation of a neotype. Bulletin of Zoological Nomenclature. 68(1), 89-90.

Monday, December 15, 2014

Gansus zheni is Iteravis

So two Jehol ornithuromorphs were just named- Iteravis huchzermeyeri and Gansus zheni.  While writing up their Database entries, I noticed Iteravis is from the new Sihedang locality, where "most of the new ornithuromorphs appear to represent a single new taxon, which we describe here."  zheni is also from Sihedang.  Hmm...

How are the papers?

First a brief comment on the papers' quality.  Both taxa are named by different groups of researchers- Iteravis by Zhou, O'Connor and M. Wang, and zheni by Liu, Chiappe, Zhang, Bell, Meng, Ji and X. Wang.  Zhou et al.'s description of Iteravis is much longer and more detailed than Liu et al.'s on zheni, though Liu et al. provide more closeups of the specimens.  One irritating thing about Liu et al.'s measurement table is that it excludes manual elements except for the carpometacarpus.  But it does waste space with previously published measurements of Gansus yumenensis.  And I just noticed now that Gansus' name is put above the wrong column, the one for the right side of zheni specimen BMNHC-Ph 1342.  Good thing we pay journals to typeset for us!  Also annoying is both papers mention specimens that are undescribed.  Zhou et al. mention "approximately 20 ornithuromorphs" from Sihedang, of which most are Iteravis, but which don't even get specimen numbers.  Liu et al. list BMNHC-Ph 1394 as a paratype of zheni, but its not illustrated, measured or described.  While there are a few things I think Zhou et al. got wrong, Liu et al. make more mistakes in both anatomy and grammar.  The main skeletal figures in Liu et al. (figures 1 and 2) have the specimen numbers switched, so figure 1 says its of BMNHC-Ph 1342 but is actually of BMNHC-Ph 1318, and the reverse is true of figure 2.  On the other hand, Zhou et al. claim they used the data matrix of O'Connor et al.'s (2011) redescription of Rapaxavis, but that paper has no phylogenetic analysis.  As far as I can tell, they actually used the matrix of O'Connor and Zelenkov's (2013) redescription of Ambiortus, which isn't even in their References list.  Both of these are pretty big blunders you would hope peer reviewers would catch.  In the analysis itself, Zhou et al. initially found one most parsimonious tree in TNT, then ran it a second time (with that first tree as the seed?) and found a whopping 9760 trees that were one step shorter.  They show both that first 847 step tree and the strict consensus of the 846 step trees, but why bother showing the less parsimonious tree that's misleadingly resolved?  And if you have a huge polytomy involving Iteravis and eight other taxa in your strict consensus, why not make any attempt to resolve it?!  It's VERY easy in TNT to remove any combination of taxa from your consensus tree and thus see which ones cause the polytomy.  My guess this time is that the fragmentary Limenavis is messing things up.  I'd check, but the authors didn't include their codings for Iteravis in the paper and there's no supplementary information.  Guess I'll be emailing Jingmai...

Zhou et al. think Sihedang is in the Yixian Formation and Liu et al. think it's in the Jiufotang Formation, and the latter seem correct as the pterosaur Ikrandraco is known from Sihedang and another Jiufotang locality.  The birds are near identical in size (femora 35 vs. 34.5-36.4 mm) and have similar morphology.  Let's compare diagnoses-

Iteravis' diagnosis

Iteravis is diagnosed by (after Zhou et al., 2014)-
A1. premaxillary corpus elongate and toothless. The premaxillary body is the same length in zheni, and lacks teeth there as well (fig. 3A, contra Liu et al. stating it is unclear whether teeth were present; see red line in my cranial figure).  Toothlessness in the premaxilla is actually a synapomorphy of birds closer to Aves than songlingornithids. 
A2. maxilla with numerous teeth.  Again stated to be uncertain in zheni by Liu et al., but five alveoli are visible in their figure 3A (see red angle in my cranial figure).  As for the tooth number, Zhou et al. merely report "several" in Iteravis, and only a couple are visible in their figure, so this matches as well.  Ornithuromorphs plesiomorphically have at least several maxillary teeth.
A3. rostrum 50% of skull length. This is also true in zheni, and in many other basal ornithuromorphs too- Archaeorhynchus, Hongshanornis, Jianchangornis, Schizooura, Longicrusavis, Yixianornis, etc..
A4. ethmoid bone lining rostral half of the orbit. Though unidentified in zheni, this is visible in figure 3B and even has the same posterodorsally angled ridge with expanded central portion (yellow lines in cranial figure).  Of course, this mesethmoid is widespread in maniraptoriforms, though rarely preserved.
A5. tubercle on caudal margin of minor digit phalanx. This is visible in zheni too (green line in my postcranial figure), though also in Yumenornis, Gansus (Li et al., 2011 fig. 2A) and Ichthyornis.  Clarke (2004) states this flexor process is also present in tinamous "and an array of other avian taxa", and as phalanx III-1 isn't preserved in other non-avian birds more derived than songlingornithids, it may be a character of this clade.
A6. pubes with dorsally expanded distal boot. The pubic boots are almost identical in Iteravis and zheni.  Boots that are dorsally/posteriorly expanded are plesiomorphic for theropods, and are found in other ornithuromorphs that retain boots such as Hongshanornis, Yanornis and Schizooura.
A7. narrow ischium with concave ventral margin and weak dorsal process at midpoint.  zheni has the same kind of ischium.  A number of ornithuromorphs have ventrally concave ischia (e.g. Chaoyangia, Schizooura, Changmaornis, Yixianornis, hesperornithines), and of these, Gansus, Piscivoravis and Yanornis have a weak mid dorsal process as well.

Skulls of Iteravis zheni. Top inset- Gansus zheni holotype BMNHC-Ph 1342. Top- Gansus zheni paratype BMNHC-Ph 1318. Bottom- Iteravis huchzermeyeri holotype IVPPV18958. Red line points to toothless premaxillary edge, supposedly uncertain in Gansus zheni.  Red angle shows possible maxillary alveoli.  Yellow line points to mesethmoid ridge similar in both specimens.  Blue line points to predentary, supposedly unpreserved in Gansus zheni. Modified after Liu et al. (2014) and Zhou et al. (2014).

zheni's diagnosis

zheni is diagnosed by Liu et al. purely by characters that supposedly distinguish it from Gansus yumenensis-
B1. broader U-shaped furcula with an interclavicular angle of approximately 60 degrees (as opposed to ~40 degrees for Gansus yumenensis).  This is untrue, as interclavicular angles in zheni are ~45 and ~53 degrees.  Iteravis' is 54 degrees and Gansus' is ~42 (listed as ~38 by You et al., 2006).  The numbers for zheni and Gansus should be taken with caution though, as their furculae are distorted.  Similar angles to Iteravis and zheni are found in Archaeorhynchus, Jianchangornis, Parahongshanornis, Hongshanornis, Schizooura, Songlingornis and Yixianornis.  Almost all basal ornithuromorphs have U-shaped furculae.
B2. cnemial crests of tibiotarsus extending distally less than in Gansus yumenensis.  This is untrue, as Gansus has a very short cnemial crest extending 4% of tibiotarsal length (excluding the apomorphic proximal extension of the crest), while zheni's cnemial crest is 15% of tibiotarsal length (not 25% as the authors state).  Iteravis' is 8% (comparable to the authors' estimate of 10%).
B3. manual digit II (major digit) proportionally shorter than in Gansus yumenensis.  Phalanges II-1+2 are 86-96% of metacarpal II in zheni compared to 102% in Iteravis.  This is compared to 81-83% in Gansus, so the character is incorrect.  Similar values to Iteravis are found in Tianyuornis (85%), Yumenornis (87%), Piscivoravis (88%), Schizooura (93%), Archaeorhynchus (91-96%) and Yanornis martini (95-107%).
B4. pedal digit IV slightly longer than digit III (pedal digit IV is markedly longer than digit III in Gansus yumenensis). The ratio (ignoring unguals) in zheni is 99-106% compared to 110% in Iteravis.  The ratio in Gansus is 110-122%, so is usually larger, but not always distinct.  Schizooura is the only other basal ornithuromorph which overlaps Iteravis/zheni, with a ratio of 100%.
B5. ratio of pedal digit III/tarsometatarsus about 1.1 (it is approximately 1.0 in Gansus yumenensis). Ignoring unguals (which are rarely measured), the ratio is 89-97% in Iteravis and 97% in zheniGansus actually overlaps this with ratios of 74-101%.  Several other basal ornithuromorphs also overlap Iteravis, such as Jianchangornis (97%), Piscivoravis (94%), Yanornis martini (94-96%) and Y? guozghangi (97%). 
B6. claws of pedal digits III and IV lacking a prominent pendant flexor tubercle (present in Gansus yumenensis).  This is also true in Iteravis and all other basal ornithuromorphs, as the flexor tubercle morphology of Gansus is an autapomorphy.

Skeletons of Iteravis zheni. Left- Gansus zheni paratype BMNHC-Ph 1318. Center- Gansus zheni holotype BMNHC-Ph 1342. Right- Iteravis huchzermeyeri holotype IVPP V18958. Yellow line points to supposed median ventral synsacral groove which is more likely taphonomic.  Green line points to flexor process on manual phalanx III-1. Purple line points to omal process on lateral coracoid, supposedly absent in Iteravis (note the impression in the matrix).  Modified after Liu et al. (2014) and Zhou et al. (2014).
Other supposed differences

You can see that given their diagnoses, Iteravis and zheni only differ in slightly different ratios that are usually closer to each other than between the two measured zheni specimens.  There are also several characters which differ in their descriptions.   

zheni is said to have a "small, rostrally tapered, and tear-shaped" external naris (mistakenly cited as the internal naris), but given the odd premaxillary shape in BMNHC-Ph 1318, the premaxilla and maxilla are probably crushed in largely ventral view (note several possible alveoli in the maxilla and the deep bone under them which would be the palatal shelf; see red angle in my cranial figure), artificially shortening and tapering the anterior narial edge.  Liu et al. state zheni's naris posteriorly overlaps the antorbital fenestra, which would barely be true in their interpretation, while the labeled nasal fragment in Iteravis suggests this isn't so in that taxon.  However, the antorbital fenestral area in both specimens is a jumble of bone fragments and multicolored sediment reflecting the fragile nature of that region in birds and the separation of slabs which exposed it.  Thus any edge of the fenestra is impossible to identify exactly.  Liu et al. claim "Unlike other Jehol ornithuromorphs [including Iteravis] ... no pre-mandibular ossification is visible in any of the two studied specimens."  This would be easily explainable by taphonomy as both skulls are rather poorly preserved and the element is small and loosely connected to the dentaries.  Regardless, there are possible predentaries in each specimen- contacting the premaxillae just in front of the dentary in BMNHC-Ph 1342 and attached to the left dentary tip projecting dorsally in BMNHC-Ph 1318 (blue lines in my cranial figure).

Liu et al. state zheni has "a broad ventral groove running along the entire exposed surface" of the synsacrum, while Zhou et al. state Iteravis has "a flat ventral surface".  The latter seems true, but the 'groove' in zheni seems to be the taphonomic collapse of the hollow interior as seen in its tibiotarsi, humeri and ulnae (yellow line in my postcranial figure).  Zhou et al. states Iteravis lacks "the cranial hook present in Gansus", while it is clearly present in zheni's coracoids.  Yet both coracoids are broken in this area in Iteravis, and the left shows a depression in the matrix which seems to indicate the hook's original presence (purple line in my postcranial figure).  Liu et al. state zheni has a "prominent and triangular-shaped laterocranial process", which is absent in Iteravis.  Yet this process is also absent in the illustrated zheni specimens BMNHC-Ph 1318 and 1342.  Liu et al. cites BMNHC-Ph 1394 as having the process, but until this specimen is illustrated, it can be considered polymorphic at best to misinterpreted at worst.  zheni is said to lack ossified uncinate processes, whereas Iteravis is reported to preserve "one probable uncinate process".  All three specimens have ribcages which are only partly articulated and exposed though, so its easily possible uncinate processes are hidden if present in zheni, or that the one was misidentified in Iteravis.  Liu et al. state zheni has a deltopectoral crest on the humerus "which extends more than one-third the total length of the bone", while Iteravis' is described as extending "the proximal one-third of the humerus", but the crest in the latter is almost entirely covered by other elements so cannot be measured.  Iteravis' carpometacarpus is described as incompletely fused versus completely fused in zheni, but the specimen is slightly smaller than zheni specimens (humeri 97% of BMNHC-Ph1318, 95-97% of BMNHC-Ph1342) so could be expected to have less fusion.  Liu et al. say zheni lacks an extensor process on metacarpal I, while Iteravis is said to have a small extensor process.  Both taxa have the same morphology though, which is comparable to the extensor flange of basal paravians and not the extensor process of some ornithuromorphs.

As noted above, the authors give very different lengths for Iteravis' and zheni's cnemial crests (10 vs. 25% of tibiotarsal length), though the real apparent values are 8% vs. 15%.  The discrepancy largely seems due to zheni's tibiotarsi being preserved in anterior view, where the collapse of the element causes a median groove that exaggerates structures on either side such as the laterally placed cnemial crest.  Iteravis' right tibiotarsus is in medial view, but the left element is partially covered by the sternum and has a taphonomic concavity that extends the apparent length of the cnemial crest.  Iteravis' fibula is described as "just over half the length of the tibiotarsus", while zheni's is said to only extend "to nearly the midshaft of the tibia."  In reality, all specimens have distal ends hidden by the tibiotarsus so cannot be exactly measured.  Liu et al. state "the proximal phalanges of all pedal digits are longer than any of their respective distal phalanges" in zheni, while Zhou et al. say Iteravis has a slightly longer II-2 than II-1.  Their own measurement table shows zheni is polymorphic for this though.  Iteravis is reported to have a pedal digit IV shorter than III in contrast to zheni, but as noted above, the ratio excluding unguals is 110% in Iteravis vs. 99-106% in zheni.  So Iteravis actually has the longer digit IV, but there's more variation in zheni than difference between it and Iteravis.

Given the lack of difference between Iteravis and zheni, they are near certainly synonyms.  Iteravis was published online October 29th vs. zheni on November 14th.  We might think huchzermeyeri wins over zheni by 16 days, except for the fact Zhou et al. didn't include a ZooBank registration.  So the physical publication time is what counts, which is December 1. Thus zheni wins by 30 days.  A good example of why people need to register their names. Still we have the question...

Is this Gansus?

Liu et al. diagnosed Gansus by-
C1. hooked omal projection of the sternolateral process of the coracoid. This is actually polymorphic in Gansus (absent in CAGS-IG-04-CM-012; O'Connor and Zelenkov, 2013), and also present in Ichthyornis.  Both are miscoded in the matrix.
C2. sternum with a caudomedially curved outermost (lateral) trabecula. This is more accurately understood as having a distal expansion of the posterolateral process that is expanded medially but not much laterally, which makes the end seem to curve medially.  It is also present in Jiuquanornis, Hongshanornis, Jianchangornis, Yumenornis and Ambiortus. Notably, this isn't actually the character coded for in the analysis, which is the angle the process projects at.
C3. intermembral index (length of humerus + ulna)/(length of femur + tibiotarsus) between 0.9 and 1.1. zheni actually falls outside of this range sometimes, with a ratio of 1.06-1.12.  Parahongshanornis (.9) and Yixianornis (1.07) also fall within this ratio.
C4. intermetacarpal space terminating distal to the distal end of metacarpal I.  This is unreliable, as it varies with metacarpal I length as well as how the laminar metacarpal III is crushed in relation to metacarpal II.  
C5. metatarsal II shorter than metatarsal IV (metatarsal II extends distally only as far as the base of the trochlea of metatarsal IV). Metatarsal II is near universally shorter than IV in basal ornithuromorphs, with their exact trochlear relation difficult to judge in specimens preserved with tarsometatarsi in dorsal view. However, metatarsal II is as short compared to IV as in Gansus or moreso in Ichthyornis and hesperornithines at least.  This is coded as such in the matrix, but the basal hesperornithines Enaliornis and Baptornis are miscoded as having longer mtIIs, as is Vegavis.  With these corrected, all included birds more derived than songlingornithids have the state, except Apsaravis and Gallus.
C6. proximal pedal phalanges longer than distal pedal phalanges. This is true in almost every basal ornithuromorph, with zheni and Gansus ironically being the only taxa with some discordant specimens (both in digit II).  Note while this is a character in the analysis, it is properly coded as present in all ornithuromorphs in the matrix so does not resolve as a Gansus character.  Why it was then included in their emended diagnosis for the genus, I have no idea.
C7. pedal digit IV longer than digit III. zheni is polymorphic for this, as noted above.  Hesperornithoids also exhibit the state, more developed than zheni or Gansus.  The character was not included in their analysis.
They also listed one other character which united zheni and Gansus in their analysis-
C8. supracoracoidal nerve foramen of coracoid displaced so that it[s] nerve no longer passes through the coracoid. Zhou et al. state this is untrue in Iteravis. The foramen is difficult to see in specimens crushed in two dimensions, so it is very possible Liu et al. miscoded zheni.  Or it may be polymorphic.  Archaeorhynchus, Jianchangornis, Patagopteryx, Hongshanornis and Longicrusavis also lack this foramen, but only the former two are coded as such in the matrix.

The total evidence here suggests C4 is invalid, C1, C3, C6, C7 and ?C8 are polymorphic in at least one those species, C5 is symplesiomorphic, and C2 is true in several other taxa.  Changing the ten miscodings noted above (with zheni conservatively coded as polymorphic for the coracoid foramen), zheni ends up basal to Gansus and birds closer to the crown.  Checking which characters supported this, I found most were based on miscodings as well*.  Correcting these left zheni basal to Gansus, supported only by its gastralia.  Yet Gansus specimens may have taphonomically lost their gastralia (e.g. no crania are connected to any), so this isn't the greatest evidence.  Enforcing zheni to be Gansus results in trees one step longer, so is basically as parsimonious.  Thus neither position is well supported, and the new combination Iteravis zheni is used until good evidence for referring it to Gansus is presented.

* Ichthyornis and Apsaravis miscoded as having fused dentaries; Gansus miscoded as having an extensor process on metacarpal I; Gansus miscoded as having a first manual digit shorter than 50% of metacarpal II length; Gansus miscoded as having a manual ungual II subequal to or longer than I; Schizooura, Gansus, Ichthyornis, Anas and Gallus miscoded as having proximodorsal ischial processes, when they have mid-dorsal processes like other ornithuromorphs (except Patagopteryx which has both and was miscoded as lacking the proximodorsal one); zheni miscoded as having 8 and/or 10 sacrals instead of ~8-10.

Finally, the 22 miscodings noted above change the ornithuromorph part of the tree.
Liu et al. had- (Arc(Pat(Vor(Schiz((Hong,Long)(Jian((Song(Yan,Yix))(Gans(Hesp(Ich(Veg,Aves)))))))))))
... with Apsaravis either just more derived than Gansus or sister to Vegavis+Aves.
The new tree is- ((Vor,Pat)(Schiz(Arc,Jian,Song,Yan,Yix(Long,Hong)(Gans(Ich(Aps(Hesp(Veg,Aves))))))))
Not that I trust the latter tree either, as 22 corrected states centered around one node changed that much, further corrections will probably have greater effects.

References- Clarke, 2004. Morphology, phylogenetic taxonomy, and systematics of Ichthyornis and Apatornis (Avialae: Ornithurae). Bulletin of the American Museum of Natural History. 286, 1-179.

You, Lamanna, Harris, Chiappe, O'Connor, Ji, Lu, Yuan, Li, Zhang, Lacovara, Dodson and Ji, 2006. A nearly modern amphibious bird from the Early Cretaceous of Northwestern China. Science. 312, 1640-1643.

Li, Zhang, Zhou, Li, Liu and Wang, 2011. New material of Gansus and a discussion on its habit. Vertebrata PalAsiatica. 49(4), 435-445.

O'Connor, Chiappe, Gao and Zhao, 2011. Anatomy of the Early Cretaceous enantiornithine bird Rapaxavis pani. Acta Palaeontologica Polonica. 56(3), 463-475.

O'Connor and Zelenkov, 2013. The phylogenetic position of Ambiortus: Comparison with other Mesozoic birds from Asia. Paleontological Journal. 47(11), 1270-1281.

Liu, Chiappe, Zhang, Bell, Meng, Ji and Wang, 2014. An advanced, new long-legged bird from the Early Cretaceous of the Jehol Group (northeastern China): Insights into the temporal divergence of modern birds. Zootaxa. 3884(3), 253-266.

Zhou, O'Connor and Wang, 2014. A new species from an ornithuromorph (Aves: Ornithothoraces) dominated locality of the Jehol Biota. Chinese Science Bulletin. 59(36), 5366-5378.

Wednesday, December 3, 2014

Norman's nomenclature's notoriously negative

Norman (2014) just published a revision of the iguanodont Hypselospinus, and while I have no opinion on the issues of synonymization, his treatment of nomenclature is deeply flawed.

First, Norman uses the term "nomen dubium in two different ways.  The correct way is illustrated by his discussion of Delapparentia, where he declares it a nomen dubium because it can't be distinguished from other iguanodonts.  This is also how he uses it for Siamodon and Penelopognathus.  However, he uses it incorrectly when he claims junior synonyms are nomina dubia.  A nomen dubium cannot be distinguished from two or more taxa, so that we can't know what it was.  But if you can't distinguish it from only one other taxon, then we know what it was and it's a junior synonym instead.  So contra Norman, he views Huxleysaurus, Darwinosaurus, Dollodon, Proplanicoxa, Sellacoxa, Mantellodon, Vectisaurus, Sphenospondylus and Kukufeldia as junior synonyms, NOT nomina dubia.  It's particularly difficult to figure out what Norman's concept of 'nomen dubium' is since there are cases where the same species is given different status depending on which genus it's paired with.  Iguanodon seeleyi and Wadhurstia fittoni are listed only as synonyms, yet Dollodon seeleyi and Huxleysaurus fittoni are listed as synonyms AND nomina dubia?!  What?  That makes no sense.

Secondly, Norman doesn't seem to 'get' phylogenetic nomenclature.  He brings up numerous ornithopod examples of how "topological change can occur in trees resulting from different systematic analyses", which is true.  He finds Tenontosaurus closer to Hypsilophodon than to Iguanodon, whereas most other modern analyses find the opposite, etc..  But then he says "Topological change will generate nomenclatural inconsistency that compromises the technique of clade anchoring. Consistency (a universal aspiration amongst taxonomists) underpins the advocacy of phylogenetic definitions but can only be assured if (and when) phylogenetic trees maintain consistent relational topologies."  This doesn't compromise the technique, it's the point of the technique!  If we all have a concept of Iguanodontia as (Iguanodon < Hypsilophodon) and Hypsilophodontidae as (Hypsilophodon < Iguanodon)*, then we can just say Norman recovered Tenontosaurus as a hypsilophodontid while Butler found it in Iguanodontia and know what that means.  The clades aren't supposed to have stable membership, they're supposed to have stable positional relationships to certain taxa.  So when Norman states Iguanodontia as defined above "is misleading in the sense that it clusters OTUs as anatomically dissimilar (dentally, cranially, and postcranially) as Tenontosaurus (and other hypsilophodontians, in the usage employed here - Figs 50, 52) with Dryosaurus and Camptosaurus that have definitively Iguanodon-like teeth", he's missing the point.  It doesn't matter how dissimilar the taxa in a clade are, the fact they form that clade with Iguanodon as opposed to Hypsilophodon is all that matters.

* All definitions I use here are simplified in not listing the type species for each genus for clarity's sake.

Norman's (2014) nomenclature on left vs. traditional/suggested nomenclature on right.  Modified after Norman (2014).

Finally we have Norman's taxa and definitions themselves.

Clypeodonta is defined as "Hypsilophodon foxii, Edmontosaurus regalis, their most recent common ancestor, and all of its descendants."  So the only non-clypeodont ornithopods are orodromines, Asian thescelosaurines and sometimes American thescelosaurines (in Boyd-based and Scheetz-based analyses but not Butler-based ones).

Norman defines Hypsilophodontia as "Hypsilophodon foxii, Tenontosaurus tilletti, their most recent common ancestor, and all of its descendants", but this is a senior synonym of Clypeodonta in most topologies since Tenontosaurus is an iguanodont in them.  It's also problematic because Hypsilophodontidae is already defined as (Hypsilophodon < Parasaurolophus) thanks to Sereno (1998).  Hypsilophodontidae thus covers the same taxa as Hypsilophodontia in Norman's cladogram, and in the absence of any proposed non-hypsilophodontian hypsilophodontids it seems unnecessary.  Note also that this puts an -ia clade inside of an -idae clade, which is unintuitive thanks to our Linnaean training.  Ironically, Cooper (1985) first proposed Hypsilophodontia as a clade equivalent to Clypeodonta.

Iguanodontia is defined as "Edmontosaurus regalis and all taxa more closely related to E. regalis than to the taxa subtended to the clade (Hypsilophodontia) that includes Hypsilophodon foxii and T. tilletti."  This is a horrible definition.  An obvious issue is that Edmontosaurus is used instead of Iguanodon, which violates Article 11.7 of the Phylocode.  The more pressing issue is that the definition is self-destructive if the consensus is correct in placing Tenontosaurus closer to Edmontosaurus than to Hypsilophodon.  If that consensus is correct, Edmontosaurus is itself subtended by the clade that includes Hypsilophodon and Tenontosaurus, so it refers to impossible taxa that are more closely related to themselves than to themselves.  Funny that after railing against definitions that only work in certain phylogenies, Norman creates a definition for a commonly used name that only works in his own heterodox phylogeny.

Ankylopollexia is redefined as "Edmontosaurus regalis and all taxa more closely related to E. regalis than to Dryosaurus altus" instead of the original (Camptosaurus + Parasaurolophus).  Why bother to redefine this when both definitions cover the same known taxa?  Also how about using a taxon with a actual pollex in the definition?  It's as if someone used Harpymimus as the internal specifier for Arctometatarsalia.

Styracosterna is redefined as "Batyrosaurus rozhdestvenskyi, E. regalis, their common ancestor, and all of its descendants" instead of the original (Parasaurolophus < Camptosaurus).  Again, both definitions cover the same taxa in Norman's cladogram, so there was no reason to make a new one.  Norman says application of the old definition "is compromised by
the increased complexity of camptosaur-grade (Camptosauridae sensu Sereno) iguanodont interrelationships (McDonald, 2011: fig. 1), as exemplified by the positions of Uteodon and Cumnoria."  But what's the problem if Uteodon and Cumnoria are styracosternans?  That's an interesting fact, and it's not like Sereno (1986) mentioned either genus when naming Styracosterna.  More importantly, why choose Batyrosaurus as your internal specifier?!  That was named 26 years after Styracosterna and found to be a hadrosauroid close to Probactrosaurus and Eolambia in its original description.  If that's right, Norman's Styracosterna would be a much less inclusive clade than historically recognized.  So again Norman creates a definition that only works in his heterodox phylogeny.  I don't know which topology is right, though Norman's does create a huge ghost lineage for the Santonian Batryosaurus if it's that basal.

Norman unofficially calls a clade of taxa 'iguanodontoids', but this clade already has a valid and defined name- Iguanodontidae.  The latter family was defined as (Iguanodon < Parasaurolophus) by Sereno (1998), so if Norman were effectively using the power of phylogenetic nomenclature, he could just say he found Proa, Jinzhousaurus, Bolong, Barilium and Mantellisaurus to be iguanodontids and we'd know what he means.

Hadrosauriformes is redefined as "Altirhinus kurzanovi, E. regalis, their common ancestor, and all of its descendants", instead of the original (Iguanodon + Parasaurolophus).   This changes the clade to be less inclusive for no reason, excluding iguanodontids.  Note both definitions violate Article 11.7, which requires Hadrosaurus to be used as an internal specifier.  Like the styracosternan situation, Norman's redefinition uses an internal specifier which was not even named when the clade was named (Altirhinus named in 1998 vs. Hadrosauriformes in 1997). 

Hadrosauromorpha is a new name for (Edmontosaurus < Probactrosaurus), which should again use Hadrosaurus as per Article 11.7.  Besides that, I think this taxon is a good one subsecting a long stem and using a classic genus.

Finally, Euhadrosauria is defined as "Parasaurolophus, Saurolophus, Edmontosaurus, their most common ancestor, and all of its descendants."  It hasn't been defined before to my (limited) knowledge, and this does correspond to the clade in Weishampel et al.'s (1993) phylogeny where they named it.  The problem is that in Prieto-Marquez-based phylogenies (which are 98% of all recent hadrosaur phylogenies), Hadrosaurus itself falls just outside this clade.  A Euhadrosauria excluding Hadrosaurus is counterintuitive to say the least.  Weishampel et al. created Euhadrosauria as "the traditional grouping of hadrosaurines and lambeosaurines", as opposed to the more basal Telmatosaurus.  Since Telmatosaurus is still considered more basal than Hadrosaurus, the phylogenetic definition (Hadrosaurus + Lambeosaurus) seems obvious.  This way it will always include the same taxa whether Hadrosaurus is in its traditional position by Kritosaurus or just basal to the main hadrosaur split.

It seems pretty obvious the ideal definitions using eponymous taxa and original concepts are-
Clypeodonta- (Hypsilophodon + Hadrosaurus)
Hypsilophodontidae- (Hypsilophodon < Hadrosaurus)
Iguanodontia- (Iguanodon < Hypsilophodon)
Dryomorpha- (Dryosaurus + Hadrosaurus)
Dryosauridae- (Dryosaurus < Hadrosaurus)
Ankylopollexia- (Camptosaurus + Hadrosaurus)
Camptosauridae- (Camptosaurus < Hadrosaurus)
Styracosterna- (Hadrosaurus < Camptosaurus)
Hadrosauriformes- (Iguanodon + Hadrosaurus)
Iguanodontidae- (Iguanodon < Hadrosaurus)
Hadrosauroidea- (Hadrosaurus < Iguanodon)
Hadrosauromorpha- (Hadrosaurus < Probactrosaurus)
Euhadrosauria- (Hadrosaurus + Lambeosaurus)

I don't know why no one's suggested those yet.  All eponymous, match original definitions except for replacing genera with standardized ones, plenty of node-stem triplets...  Phylogenetic nomenclature isn't rocket science.

Reference-  Norman, 2014. On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna). Zoological Journal of the Linnean Society. DOI: 10.1111/zoj.12193

Sunday, November 9, 2014

SVP 2014 Day 4

Brink et al. have a poster on Bathygnathus, which I blogged about here as an ex-theropod.  Turns out Case was right in 1905 that it belongs to Dimetrodon, as Brink et al. found it to be nested within that genus and sister to D. grandis.  This is problematic, since Bathygnathus was named 25 years before Dimetrodon, so the ICZN will need to be petitioned if we are to retain the latter genus.

Zanno et al. present a poster on what was previously reported by Zanno (2008) as another Falcarius bonebed in the Cedar Mountain Formation of Utah, but which seems to be a more derived therizinosaur now.  Originally differences were thought to be ontogenetic, but size comparisons and histology disproved this.  In the new taxon, "the more prominent development of the altiliac condition of the ilium, large distal boot of the pubis measuring more than half the pubic length, relatively straight and acuminate symphyseal aspect of the dentary, reduced recurvature of the dentary teeth, and marked ventral displacement of the mandibular condyle of the quadrate appear distinct."

Larson et al. performed a morphometric analysis of Dinosaur Park coelurosaur frontals, and found that supposed therizinosaur frontal CMN 12355 grouped with Troodon, so is troodontid instead.  Since Erlikosaurus wasn't included, I'm not sure how powerful this analysis is however.  They say CMN 12355 "shares the following features with Troodon: a shallow lateral wall defining the fossae for the olfactory system, the exclusion of the supratemporal fossa from the dorsal surface of the frontal, and a raised orbital rim."  Yet Erlikosaurus also has a shallow lateral olfactory wall (Lautenschlager et al., 2014), both therizinosaurs and troodontids are polymorphic for raised orbital rims (e.g. present in Falcarius and the Nanchao therizinosaur embryo, absent in Sinornithoides), and Troodon, Erlikosaurus and CMN 12355 all have dorsal exposure of the supratemporal fossa.  They further state CMN 12355 "differs from the holotype of Erlikosaurus (IGM 100/111) in the construction of the lacrimal-frontal joint", and indeed the prefrontal-frontal articular surface in Erlikosaurus (which doesn't even have lacrimal-frontal contact) isn't exposed dorsally, unlike the contact in Troodon and CMN 12355.  In comparing them myself, CMN 12355's orbital outline resembles Erlikosaurus more, but the supratemporal fossae are intermediate in their separation.  Ventrally, the less anteriorly expanded olfactory bulbs and more posteriorly expanded cerebral fossae are similar to Troodon, but the prefrontal/lacrimal facet is placed far more anteromedially then in either Troodon or Erlikosaurus.  So in the end I'm not convinced either way, and think CMN 12355 might belong to something else entirely.  Larson et al. state "this removes the only record of a therizinosaur from the well-sampled Campanian-Maastrichtian fossil record of North America, suggesting the extinction of this group in North America prior to the Campanian,", but besides two more Dinosaur Park frontals referred to therizinosaurs by Currie (1992, 2005), there's also the pedal ungual RTMP 79.15.1 he mentions.  Ryan and Russell (2001) list a cervical from the Scollard Formation of Alberta (RTMP 86.207.17), and Russell (1984) reported a therizinosaurid astragalus from the Hell Creek Formation of Montana [EDIT 2 on 2-15-15- Russell and Manabe 2002 indicate this element is actually the Tyrannosaurus quadrate initially misidentified as a quadrate by Welles and Long].  So maybe these other records are misidentified too, but there's more work to be done before we can reach Larson et al.'s conclusion.

Supposed therizinosaur or troodontid frontal CMN 12355 (after Sues, 1978).  Ventral (left) and dorsal (right) views.

Allain reports a new Ichthyovenator specimen which preserves "the complete cervical skeleton and the first dorsal vertebra, as well as the left pubis, seven additional caudal vertebrae and three teeth."  Interestingly, "the first dorsal vertebra of Ichthyovenator is nearly identical to the holotypic vertebra of the enigmatic theropod Sigilmassasaurus brevicollis", so there's more evidence Sigilmassasaurus is Spinosaurus.  "In addition to the peculiar morphology of posterior cervical and anterior dorsal vertebrae, the straight unserrated crowns of the teeth of Ichthyovenator suggest it is more closely related to Spinosaurinae than previously thought."  Since my analysis including Ichthyovenator in partially corrected versions of Allain et al.'s and Carrano et al.'s matrices found it to take 0-2 more steps to be a spinosaurid than a carnosaur, and this new data provides those extra steps, I now agree the genus is spinosaurid and possibly spinosaurine.

McFeeters et al. do a rather cool thing and examine reports of ornithomimids from Foremost, Oldman and Milk River Formations of Western North America.  They find pedal material from the Foremost and Oldman Formations, but the older Milk River and Foremost Formations have no definite ornithomimid material.  Previously reported and catalogued material from there is indeterminate or misidentified, with "the only described specimen previously referred to Ornithomimidae" (I assume the RTMP pedal phalanx reported by Ryan and Russell in 2001 the CMN pedal phalanx in plate II figure 10 of Russell, 1935) being more similar belonging to probable Orodromeus synonym "Laosaurus" minimus a 'basal ornithopod' (so probably a thescelosaurid)The lead author notes below in a comment it is also similar to a phalanx referred to Elmisaurus though, so its identity remains uncertain for now.  They suggest "the Late Cretaceous ornithomimid clade did not migrate into Laramidia until the beginning of the Late Campanian", which is possible, but I wonder just how much Foremost and Oldman material they found.  After all, I'd say ~ 99% of paravian remains from these sediments are teeth, so remains of toothless taxa like ornithomimids are going to be rare by default and might not have been collected yet if the sample size is low.  But if later formations preserve many thescelosaurid and ornithomimid pedal elements and earlier formations only preserve many thescelosaurid pedal elements and no ornithomimid ones, the statistical argument seems valid.

Lu et al. (misspelled as La in the abstract book) report yet another new oviraptorid from the Nanxiong Formation in addition to the prefix-triangle of Ganzhousaurus nankangensis, Nankangia jiangxiensis and Jiangxisaurus ganzhouensis, as well as the juvenile Banji long.  These all actually fall out in different parts of the tree in the Lori analysis, and at least three do in the Anzu analysis, so maybe they're all valid.  This new taxon is known from a partial skeletopn with incomplete skull and mandible and is "characterized by an anterodorsally sloping occiput and quadrate (shared with Citipati), a small circular supertemporal fenestra (much smaller than the lower temporal fenenstra), and the dorsal margin of the dentary above the external mandibular fenestra is strongly concave ventrally."  In what I assume is a version of the Maryanska et al. analysis used in all current oviraptorosaur papers, it falls out sister to Citipati.  This matches one of the named Nanxiong species in the Lori analysis, so maybe we finally have a synonymy.  Might I suggest we start a new prefix-triangle and name this one 'Longia nanxiongia', then the next named species can be 'Nanxiongsaurus banjiensis'.

Button et al. have a poster on a new coelurosaur found in 2012 what was originally listed as "Ornithomimidae? new genus and species" by Kirkland et al. in 1998 from the Mussentuchit Member of the Cedar Mountain Formation of Utah.  Turns out this is an "associated right hind limb consisting of a partial femoral shaft, nearly complete tibia, distal two-thirds of metatarsal IV, and pedal phalanges IV-2 and IV-4."  While arctometatarsalian, "metatarsal IV most resembles Coelurus (YPM 2010) from the Upper Jurassic Morrison Formation in general proportion, mediolateral compression of the distal aspect, and near absence of a lateral collateral ligament pit, yet is unique in possessing an obliquely oriented groove marking the extensor surface and a dorsally bulbous distal condyle."  Is this an ornithomimosaur, coelurid, or something else like a troodontid?  Scheetz et al. had an SVP abstract in 2010 about a basal coelurosaur convergent on ornithomimosaurs from the Yellow Cat Member of this formation, but that has a non-arctometatarsalian pes, so may be unrelated.  We'll have to see.

Poust et al. present the tenth supposed new Jehol microraptorian species, D2933 from the Jiufotang Formation.  This "possesses several autapomorphies, including more than 29 tail vertebrae, inclined pneumatic foramina on the dorsal vertebrae, and an unusually large coracoid fenestra", and is supposedly sister to Sinornithosaurus  The Cryptovolans holotype has 28-30 caudals, other Microraptor specimens often have about 26, and no complete tail is known in described Sinornithosaurus.  While the Microraptor hanqingi specimen lacks inclined dorsal pleurocoels (I assume that means anterodorsally oriented), we don't know the condition in any other described microraptorian specimen.  Finally, I don't know how big the supracoracoid fenestra is in D2933, but Sinornithosaurus specimens have fenestrae varying in size between 27 and 35 percent of coracoid height.  Poust et al. state "all visible neurocentral sutures, and proximal tarsals remain unfused. The porous surface texture of the cortical bone and poor ossification of long bone articular surfaces further supports an immature status. Histologic samples of the tibia, fibula, and humerus confirm that it was about one year old and still growing at death."  As D2933 is smaller than Sinornithosaurus, differences could be ontogenetic, and indeed increased ossification with age could shrink the supracoracoid fenestra's size.  It has "filamentous feathers, pennaceous feathers extending from the fore- and hindlimbs, and two long plumes extending more than 12 cm beyond the caudal series", which the authors contrast with Sinornithosaurus that shows "only branching filamentous feathers."  They propose "that this simplified condition is a secondary loss of feathers, either as a feature of the genus [Sinornithosaurus], or as part of an ontogenetic loss of 'advanced' feather types in adults."  Or maybe it's taphonomic, as described Sinornithosaurus specimens are disarticulated.  Much as with Lefevre et al.'s talk, I think we need a Lagerstatten rule for dinosaurs- 'Do not ascribe to phylogeny that which can be explained by taphonomy'. 

Kobayashi et al. present a poster on what I assume is a specimen of "Gallimimus" mongoliensis that's basically identical to their 2007 SVP abstract, so I hope we see this taxon published soon.

Gerke and Wings have an interesting study of Late Jurassic German theropod teeth.  "Four Langenberg Quarry teeth, previously assigned to velociraptorine dinosaurs, are removed from Dromaeosauridae and regarded as belonging to Tyrannosauroidea, Neotheropoda and Megalosauridae based on their dental characters."  Maybe their DFA analysis could be used to classify other supposed dromaeosaur teeth that plague studies depending on Dinosaur Park morphologies.  

Malafaia et al. present information on a new Lourinha megalosauroid specimen represented by "several cranial fragments including an incomplete left maxilla."  Several characters differ from Torvosaurus, known there from T. gurneyi.  So this may be Lourinhanosaurus, which is coelurosaurian in Carrano et al.'s tetanurine matrix partly due to miscoding it as lacking a pubic obturator fenestra.

Velocipes guerichi holotype proximal fibula in a (lateral), b (posterior), c (medial) and d (anterior) views, with proximal view on top and cross sections at right (after Huene, 1932).
Czepinski et al. had a poster on Triassic dinosaurs from Poland, which is one of my favorite kinds of papers- reevaluating historical taxa.  Middle Triassic supposed dinosaurs can't even be referred to Dinosauromorpha, but "new analysis of the Velocipes guerichi holotype from Kocury site (Silesia) suggests that it is probably the proximal part of an elongated and flattened fibula of a neotheropod dinosaur."  So Huene was right 80 years ago, whereas Rauhut and Hungerbuhler (2000) listed it as Vertebrata indet.?!  Because it was plausibly a fish?  One negative effect of cladistics is that some authors (Nesbitt et al., 2007 *cough*) only use characters coded in an analysis to classify specimens, when plenty of other differences exist between clades.  I'm glad Czepinski et al. didn't follow this method.  Now we just need a good reexamination of Avipes, Dolichosuchus and Halticosaurus.

That's it for SVP 2014.  Hope you enjoyed my theropod rundown.

Edit: Thanks to Brad McFeeters for correcting some of the information here, with the corrected info bolded above and the original wrong text crossed out.  It's like peer review for blogs. :)

Saturday, November 8, 2014

SVP 2014 Day 3- drepanosaurs and sauropods

Okay, it's become apparent this day by day format is flawed because similar talks are grouped together at SVP.  This year, basically all of the interesting theropod talks/posters were on Wednesday and Saturday.  So tomorrow's post should be huge, but here's a couple interesting of ones from today.

Pritchard and Nesbitt report on a 3D drepanosaur braincase from the Ghost Ranch quarry.  Many of its characters "are surprisingly plesiomorphic (e.g., squamosal with massive descending process, quadrate lacking posterior concavity, occipital condyle with notochordal pit), sharing more in common with non-saurian diapsids than early archosauromorphs."  "A phylogenetic analysis of 300 characters and 40 early diapsids supports the hypothesis that drepanosaurs fall outside of Sauria."  Wouldn't it be funny if pterosaurs were related to drepanosaurs, and thus non-saurians convergent on archosaurs?  Even crazier than them being lizards.  Also relevant is Paul's (2002) idea Protoavis' type braincase is from a drepanosaur, but Protoavis lacks a ventral squamosal process or a notochordal pit, though its quadrates are straight to slightly concave.  So the braincase still seems closest to derived theropods.

Madzia and Borsuk-Bialynicka have a talk titled "New sauropod material from the Nemegt Formation supports the conspecificity of Opisthocoelicauda skarzynskii and Nemegtosaurus mongoliensis."  That's an idea Paul supported in his 'field guide', but has generally been considered unlikely to undemonstrable given known remains- a skull for Nemegtosaurus and skeleton lacking neck and skull for Opisthocoelicaudia.  Alas, this presentation only says two caudal centra and five pedal unguals were found in the Polish-Mongolian expedition collections, from three different sites in the Nemegt.  The unguals "strongly resemble those of O. skarzynskii in their crescent-shaped morphology, great bilateral flattening, and generally subtriangular cross-sections adjacent to their proximal articular surfaces", while the centra "are slightly opisthocoelous and subcircular in cross-section."  That's great, but are other titanosaur unguals different?  Nor is Opisthocoelicaudia the only titanosaur with opisthocoelous caudals.  See Borealosaurus for instance.  They say "Since the postcranial elements provide no evidence for the presence of more than one titanosaur in the mid- Maastrichtian of the Nemegt Formation, there is no reason to assume that the type of N. mongoliensis belongs to a different species."  This is highly flawed reasoning.  We have at best three caudal specimens including the Opisthocoelicauda holotype.  The likelihood all three are from one species if two species lived there is pretty high, 25% if my vestigial stat skills are correct (if they were equally abundant, equally likely to be fossilized there, etc.).  Just look at another case of large Nemegt dinosaurs- Deinocheirus and Tarbosaurus.  The ZPAL has 35 Tarbosaurus but only one Deinocheirus (well, none now since it was moved to the IGM).  Even if all of those caudals and unguals are diagnostically Opisthocoelicaudia and from different individuals, that's still only 8:1 for Opistho vs. Nemegt compared to 35:1 for Tarbo vs. Deino.

Friday, November 7, 2014

SVP 2014 Day 2

Continuing from yesterday...

Not a theropod talk, but something very cool indeed.  Does anyone remember Chatterjee's supposed pachycephalosaur domes from the Triassic Maleri Formation of India?  They've never been published, but he apparently mentioned them in his SVP 1998 talk "Dinosaurs in the land of gonds."  There was some talk about them on the DML in 2000 where Weinbaum says they "look exactly like" pachycephalosaur domes, and Olshevsky mentioned Goodwin would classify them as pachycephalosaurian if they were found in the Cretaceous.  Indeed, Goodwin is listed as working with Chatterjee on Indian pachycephalosaurs in the latter's CV.  Well it looks like the mystery has been solved.  Stocker et al. report finding a basal archosauriform from the Dockum Group with a dome convergent with pachycephalosaurids.  "Like pachycephalosaurs, this Triassic specimen preserves a thickened and domed skull roof with obliterated cranial sutures, an expanded posterior margin of the skull (a synapomorphy of Marginocephalia), and large orbits."  They don't mention the Maleri specimen, but the connection seems obvious.  How ironic this was found in the Dockum, where Chatterjee did tons of work.

Makovicky et al. have a poster on dinosaurs from the Mussentuchit Member of the Cedar Mountain Formation in Utah and report on the partial skeleton of a giant oviraptorosaur.  They say "a midcaudal vertebra is highly pneumatic, and a series of four distal caudals form a pygostyle-like structure", so it's probably a caenagnathoid or close relative.  This is interesting, as the material is Albian, so is earlier than known caenagnathoids.  Because Macroelongatoolithus shells were found close by, the presenters think it may belong to this taxon.

Again not theropodan, but just amusing.  On page 137, Gerwitz and Green had an abstract about change in size throughout time in Florida deer bones, but there's a huge WITHDRAWN plastered over it.  Apparently it was supposed to be a poster on Thursday.  I've never seen a withdrawn presentation at SVP, and wonder what the story is behind what seems like an innocuous statistical study.

Good thing I padded this entry, since it seems Thursday was basically bereft of Mesozoic theropod talks.  In other news, I finished coding Deinocheirus today and it emerged in a different position than found by Lee et al. or Andrea's post.  Maybe the Angeac taxon or Datanglong will affect things, so I'm adding them now.

Thursday, November 6, 2014

SVP 2014 Day 1

Hi everyone.  Sorry about the lack of posts- coding ornithomimosaurs in the Lori matrix.  We'll see where Deinocheirus ends up.  Also, that new Erlikosaurus cranial description with fully rotatable 3D elements that you can separate and view any cross section of- coolest theropod osteology ever.  Everyone should be doing that with their material.  But hey, SVP started.  No, I'm not in Berlin, but I figured I'd report on cool theropod abstracts.  The embargo states we can't post about them until the talks have been given, and it's now Thursday in Berlin, so let's cover Wednesday's interesting talks and posters.

Dyke et al. are presenting on Balaur being an avialan instead of a dromaeosaurid, which I agree with.

Rauhut and Foth suggest Juravenator has "a number of characters shared with basal theropods, such as the presence of a posterior pleurocoel in the cervical vertebrae, a lateral brevis shelf that is continuous with the supraacetabular crest and a well-developed antitrochanter in the pelvis..."  Very interesting.  Those are ceratosaur-grade characters, which would make it even more basal than the supposedly megalosauroid Sciurumimus.  They say "Recently discovered casts [of the Compsognathus longipes holotype] show that the specimen is better preserved than first described and provide new data on its morphology, indicating that it is not the same taxon as the French Compsognathus."  I'd love a redescription since Ostrom's 1978 publication, but I think these Lagerstatten theropods are always oversplit, so color me doubtful.  Especially since they say Archaeopteryx "includes probably at least three, and as many as four to five species."

Speaking of which, Kundrat et al. CT scanned the Daiting (8th) Archaeopteryx specimen and found "the internasal and interfrontal sutures are obliterated in the Daiting specimen in contrast to the Eichstätt and Thermopolis specimens which are of similar size. This and numerous other cranial features that distinguish the Daiting specimen from the other specimens of Archaeopteryx suggest that it may represent a new species."  We'll have to see what those numerous other features are, and the fact the Daiting specimen is from a younger formation than the others gives some a priori reason to expect a new species, but sutures are often destroyed by taphonomy (e.g. Apsaravis' apparent notarium), so I'll need better evidence than that considering how crushed the skull is.

Lefevre et al. report three new paravian specimens from the Tiaojishan Formation of China, the same formation as Anchiornis, Aurornis, Eosinopteryx and maybe Xiaotingia.  All of these emerge as basal Avialae in their analysis, though at least one is stated to have troodontid characters, and we know how easily all of these Tiaojishan taxa switch positions.  Interestingly, Eosinopteryx is said to be immature based on histology despite the original description stating "the holotype of Eosinopteryx had reached a late ontogenetic stage (subadult or adult): neurocentral sutures are closed on all exposed vertebrae and the suture between the astragalus–calcaneum complex and the tibia cannot be discerned."  I'd caution again that taphonomy can hide sutures, and think that the situation here will prove similar to the Solnhofen one- the specimens will all be different from each other in ways that suggest individual and ontogenetic variation.  If not ontogenetic, the plumage variations are bound to be taphonomic.  The Lori analyses does suggest one of these taxa is distinct and not what we think it is, but that will have to wait...

Stiegler et al. (with Xu as a coauthor) state "Optimization of manual characters suggests that the manual morphology of Limusaurus is unlikely to be representative of the averostran ancestor as previously hypothesized."  Which might translate as 'we were wrong that the reduced manual digit I means tetanurines lost digit I', and yet they say "we argue that the presence of bilateral digit reduction in Limusaurus and other ceratosaurs remains a key piece of evidence for understanding theropod digit homologies."  So from the abstract, that sounds like saving face.

Foth et al. say that in Sciurumimus, "Along the dorsal side of the tail the skin is decayed, revealing a horizontal meshwork of thick, short, wrinkly filaments overlain by an outer skin layer. Due to their different morphology and different luminescence, we interpret these filaments as remains of collagen fibers from the dermis, covered by epidermis, rather than as feathers."  See, Lingham-Solier-  collagen can be preserved, but it's not feathers.  Wish the guy would buy a high-resolution camera.

Funston and Currie reveal Elmisaurus rarus has a cranial crest, and agree with me that Leptorhynchos is unnecessary.

Tanaka et al. present a poster on the Japanese hesperornithine.  Seems it would fall within Hesperornis sensu lato as far as the Database is concerned.

Dal Sasso et al. present a poster on new cranial remains of Razanandrongobe, which suggest it's a basal mesoeucrocodilian.  One more potential theropod down.

Holtz et al. have a poster which includes a new probable Anzu specimen from the Hell Creek of Montana.  It "includes distal hindlimb, pelvic elements, dorsal ribs, and caudal vertebra. Given the origination of these bones relative to the local outcrop, it seems quite likely that more the skeleton is preserved and is slated for field recovery."  Excellent.

Thursday info coming next...

Wednesday, September 17, 2014

No giant Egyptian Deltadromeus

The Spinosaurus news has led to me reviewing the African mid Cretaceous taxa on the Database.  This means I've been working my way through the untranslated Stromer (1934), which describes Spinosaurus B and Bahariasaurus among other theropod remains. The result is that what I thought I knew about the supposed giant Deltadromeus remains described there is wrong.  The recent literature would have you believe it's a partial skeleton (Carrano and Sampson, 2008) identical (Sereno et al., 1996) to the Deltadromeus holotype.  Not so.

Sereno et al. (1996) referred the Baharija 'IPHG 1912 VIII' (described by Stromer, 1934) to Deltadromeus, specifying a coracoid, pubes, femur, proximal tibia and fibula as the material. Yet this specimen number corresponds to 32 specimens described by Stromer. The coracoid IPHG 1912 VIII 60 was associated with a scapula that shares that number, the femur is IPHG 1912 VII 69 based on the size Sereno et al. reported, and the fibula must be IPHG 1912 VIII 70 as no others are reported. Yet the pectoral girdle was found in layer m while the femur and fibula were found in layer p. The only proximal tibia reported is IPHG 1912 VIII 78, which is far too small to belong with the other hindlimb elements and from a different locality. Finally, the only pubes with that number are IPHG 1912 VIII 81, which are from yet another locality and much smaller than even the tibia. This materials list agrees with Carrano and Sampson, though note contrary to their statement, it is not a "partial postcranial skeleton". Stromer used the pubes as a paratype of Bahariasaurus, questionably referred the pectoral girdle, femur and fibula to the taxon as they cannot be compared to the holotype, and referred the tibia to aff. Erectopus. Thus all material was not referred to Bahariasaurus, contra Sereno et al..

Comparison of Baharija elements on the left to Deltadromeus holotype on the right, scaled to match in size.  From left to right- pectoral girdles in lateral view, proximal femora in lateral view, tibiae in proximal view, and proximal fibulae in medial view. Modified from Stromer (1934) and Sereno et al. (1996).

The Baharija pectoral girdle actually lacks the anteroposterior expansion considered diagnostic for Deltadromeus by Sereno (length excluding posteroventral process 117% of height vs. 150% in Deltadromeus), which is also found in Elaphrosaurus and Limusaurus. Due to breakage of the posteroventral process, it's uncertain if the coracoid's subacromial notch ('notch in anterior margin' of Sereno et al., as it is the only notch in Deltadromeus' coracoid) is shallow as in Deltadromeus or deeper as in Elaphrosaurus and Limusaurus. Though again, a shallow notch might not be diagnostic of Deltadromeus as it is also found in Ceratosaurus. The pectoral girdles also differ in other ways if scaled to similar overall size, with Deltadromeus having a narrower scapular shaft, a more abruptly expanded acromion, smaller glenoid, and deeper posteroventral process.

Sereno et al. also diagnose Deltadromeus based on its "accessory trochanter" on the distal femoral shaft, which is presumably the mediodistal crest anteriorly. This is common in basal theropods like ceratosaurs (e.g. Berberosaurus, Elaphrosaurus, Limusaurus), but rarer in Coelurosauria which Sereno et al. referred Deltadromeus too. The development of the mediodistal crest is unclear in the Baharija femur. Carrano and Sampson (2008) equated the "accessory trochanter" of Sereno et al. to the M. adductor femoris 1 insertion scar on the posteromedial distal shaft, but this region is unillustrated in the Baharija femur. Finally, the Bajarija femur does have an anterior process on the lateral margin of its medial condyle, stated as diagnostic of Deltadromeus and hinted at in Sereno et al.'s skeletal reconstruction. Carrano and Sampson equated this with the mediodistal crest discussed above, but that projects largely laterally so is probably not the feature Sereno et al. had in mind. While the anterior process could indicate a relationship between the Baharija femur and Deltadromeus, the latter differs in having a fully medially oriented head and an anterior trochanter that extends distally to the fourth trochanter. The Baharija femur is 165% the size of Deltadromeus, which could lead to questions of ontogenetic change, but neither of these characters are known to change ontogenetically in theropods, and they would leave the older specimen with the more basal morphology, which is unlike at least some theropods (tyrannosaurids, dromaeosaurids).

The tibiae are more similar to each other than to Elaphrosaurus, Camarillasaurus, Ceratosaurus or Eoabelisaurus in proximal view (the only available for Deltadromeus), with Deltadromeus differing in having a smaller, triangular posterior groove and larger lateral condyle. The fibulae are roughly similar, though Deltadromeus has a more projected anteroproximal corner and a proximomedial fossa that is less proximally extensive. The supposed pubes of Deltadromeus are actually ischia (Longrich pers. comm. and DML; Carrano and Sampson, 2008), so cannot be compared to the Baharija pubes.

Thus in total, the pectoral girdle and femur are near certainly not Deltadromeus (contrary to Sereno et al.'s claim the remains are identical), the tibia and fibula could be although no described apomorphies are shared, and the pubes cannot be compared. Coincidentally only the pubes can be compared to Bahariasaurus, though they differ markedly from that taxon*. This makes it quite possible Stromer was right in referring the pectoral girdle and femur to Bahariasaurus, and also possible the tibia and fibula belong to that genus. It also may make it more likely the pubis does belong to Deltadromeus, which might get support from study of its undescribed pubic fragments. Because none of the Bajarija material can be said to be more similar to Deltadromeus than the sympatric Bahariasaurus and some are certainly not Deltadromeus, none should be referred to either genus. This also eliminates any evidence Deltadromeus reached gigantic sizes, as there is no evidence the holotype is immature and the completely fused ischial boot would argue against this.

* Bahariasaurus has a less conspicuous and more proximally placed lateral flaring (15% down the shaft, compared to 21%), the distal end is not flared laterally, there is an extensive separation of the pubic shafts distally, and the interpubic foramen is more distally placed (80% down the shaft, vs. 71%).

References- Stromer, 1934. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharije-Stufe (unterstes Cenoman). 13. Dinosauria. Abhandlungen der Bayerischen Akademie der Wissenschaften Mathematisch-naturwissenschaftliche Abteilung, Neue Folge. 22, 1-79.

Sereno, Dutheil, Iarochene, Larsson, Lyon, Magwene, Sidor, Varricchio and Wilson, 1996. Predatory dinosaurs from the Sahara and Late Cretaceous faunal differentiation. Science. 272(5264), 986-991.

Carrano and Sampson, 2008. The phylogeny of Ceratosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology. 6, 183-236.

Thursday, September 11, 2014

Spinosaurus surprise

This is a post to discuss some implications of today's huge Spinosaurus reboot by Ibrahim et al. (2014).

What a cool and unexpected morphology.  Stromer was right about the tiny pelvis all along!  With Sigilmassasaurus and bone taxa G, I and J of Russell (1996) as Spinosaurus, we have so much more data now.  Seems Lapparent (1960) had a lot of Spinosaurus material in his Carcharodontosaurus referred specimens (manual phalanx and pedal ungual from Alrar; manual ungual from Dijoua; pedal ungual from from In Abangarit).  These would have been the first Spinosaurus specimens described after Stromer's work and the destruction of the originals in WWII.

MNNHN specimens of Spinosaurus described as Carcharodontosaurus by Lapparent (1960).  1- Distal manual phalanx from Alrar, Algeria initially misidentified as a metatarsal. 11- Manual ungual from Dijoua, Algeria.  12- pedal ungual from Alrar, Algeria.  From Lapparent (1960).

Also interesting is that Medeiros and Schultz (2002) described two caudals from the Alcantara Formation of Brazil as Sigilmassasaurus.  Now that we know these are spinosaurid, they're probably the first postcrania of Oxalaia

Distal caudal vertebra UFMA 1.10.240 probably referrable to Oxalaia, described by Medeiros and Schultz (2002) as Sigilmassasaurus.  From Medeiros and Schultz (2002).

Finally, with the differences noted by Russell between Kem Kem and Baharija 'Sigilmassasaurus', and those visible between the Kem Kem neotype and Baharija Spinosaurus B, it seems possible the aegyptiacus neotype is not conspecific with the Baharija aegyptiacus holotype.  Awkward.  Interestingly, Russell viewed the Kem Kem form as more derived, and this matches some aspects of Ibrahim et al.'s figure S2 comparison between Spinosaurus B and the neotype- the neotype has a narrower distal femur with more elongate condyles (A below), and flatter pedal unguals (D below).  Was it more adapted to swimming than the Baharija Spinosaurus?

Comparison of Baharija Spinosaurus B (IPHG 1922 X45) in yellow with Kem Kem Spinosaurus aegyptiacus neotype (FSAC-KK 11888) in gray.  After Ibrahim et al. (2014).

References- Lapparent, 1960. Les dinosauriens du "Continental intercalaire" du Sahara central. Memoirs of the Geological Society of France. 88A, 1-57.

Russell, 1996. Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco. Bulletin du Muse'um national d'Histoire naturelle. 18, 349-402.

Medeiros and Schultz, 2002. A fauna dinossauriana da Laje do Coringa, Cretáceo médio do Nordeste do Brasil. Arquivos do Museu Nacional. 60(3), 155-162. 

Ibrahim, Sereno, Dal Sasso, Maganuco, Fabbri, Martill, Zouhri, Myhrvold and Iurino, 2014. Semiaquatic adaptations in a giant predatory dinosaur. Science. DOI: 10.1126/science.1258750

Monday, May 26, 2014

Is Thecocoelurus an ornithomimosaur?

Allain et al. (2014) recently claimed Thecocoelurus, a small partial theropod cervical vertebra from Early Cretaceous England, is "morphologically identical" to an undescribed supposed ornithomimosaur from the Early Cretaceous of France (from here on called the Angeac taxon).  After reading Andrea Cau's post on the topic, I decided to do some in depth comparison.

Besides the Angeac taxon, Thecocoelurus has been compared to several taxa with surprisingly similar cervical vertebrae- caenagnathids (Naish et al., 2001; Naish and Martill, 2002); Falcarius (Kirkland et al., 2004; Zanno, 2010a); and noasaurids (Naish, 2011).  These all have elongate amphicoelous cervicals with low neural spines, anterior peduncular fossae, two pairs of pleurocoels and a transversely concave ventral surface defined by lateral ridges confluent with the parapophyses.  Which is most similar to Thecocoelurus?

Naish et al. (2001) and Naish and Martill (2002) both argue it is closer to oviraptorosaurs than to therizinosauroids based on the rounded pleurocoel and thin neural spine, but this is also the case in basal therizinosaurs (Falcarius, Jianchangosaurus) (as noted by Zanno, 2010a) and noasaurids. Naish (2011) on the other hand, felt "the idea that large caenagnathids were present in Western Europe during the Barremian is difficult to reconcile with what we know of oviraptorosaur biogeography and distribution", thus favored an abelisauroid identity (I suppose based on Genusaurus).  I'd argue basal oviraptorosaurs could and do have similar morphologies (e.g. the Early Cretaceous Similicaudipteryx) and that small theropod diversity in Cretaceous Europe is very poorly known. 

Allain et al. make two new comparative arguments for Thecocoelurus being closest to the Angeac taxon.
1. They distinguished both from Noasaurus based on their concave anterior central surface, but this is true in Masiakasaurus as well. It is also true of all coelurosaurs being compared.
2. They also paired Thecocoelurus with the Angeac taxon based on pneumatic foramina above the prezygapophyses which invade the neural arch. Yet these are present in cervicals 6-10 of Masiakasaurus (Allain et al. state they are "in a modified form" but don't elaborate), at least cervical 9 of Heyuannia, and in Conchoraptor and "Ingenia" (Lu, 2004; contra Allain et al.'s claim they are unknown in oviraptorosaurs). They are also only present on the left side of Thecocoelurus (pf? in figure below, lower left), further posterior than in at least Masiakasaurus and the Angeac taxon, perhaps suggesting breakage of a naturally hollow area or pneumatic asymmetry. The only preserved posterior cervical of Falcarius doesn't preserve this area, nor does the illustrated and best preserved cervical of Chirostenotes.

So let's compare!  Contra Naish and Martill, the specimen resembles posterior cervicals more than anterior ones, and indeed the supposedly identical Angeac vertebra matches the seventh or eighth of Harpymimus based on elongation, central articular surface orientation, prezygapophyseal length and orientation, etc. (contra Allain et al.).

Anterior half of posterior cervical vertebrae in (descending) right lateral, anterior, ventral and dorsal views.  From left to right- Thecocoelurus holotype (after Naish and Martill, 2002); Angeac taxon ANG 10/175 (after Allain et al., 2014); Falcarius UMNH VP 14657 (after Zanno, 2010b); Masiakasaurus FMNH PR 2481 (after Carrano et al., 2011); Chirostenotes or Epichirostenotes ROM 43250 (after Sues, 1997); Similicaudipteryx holotype (after He et al., 2008).

The elongate parapophyses resemble Falcarius, Chirostenotes and Similicaudipteryx more than Masiakasaurus or the Angeac taxon.
The anterior pleurocoels are placed in an obvious fossa, like Falcarius and the Angeac taxon, but unlike Masiakasaurus, Chirostenotes or Similicaudipteryx.
The infradiapophyseal fossa is developed as an elongate groove, as in Falcarius but unlike Masiakasaurus, the Angeac taxon, Chirostenotes or Similicaudipteryx.
The centrum is taller than wide (midline height / width minus parapophyses 133%) as in Falcarius (118%), but unlike the Angeac taxon (95%) and especially Chirostenotes (74%) and Masiakasaurus (64%).
The anterior peduncular fossae are well defined as in Chirostenotes and at least anterior Falcarius cervicals, but unlike Masiakasaurus or the Angeac taxon. They are however also well defined in anterior Masiakasaurus cervicals, so the condition in Falcarius isn't necessarily better than that genus or the Angeac taxon.
They are also placed far below the diagonal prezygapophyseal surface as in at least anterior Falcarius cervicals, but unlike the Angeac taxon, Chirostenotes or Masiakasaurus. The same could be said re: anterior Masiakasaurus cervicals.
The prespinal fossa is broad like Chirostenotes and Masiakasaurus but unlike the Angeac taxon.
It has anteroposteriorly broad exposure dorsally as in the Angeac taxon and at least anterior Falcarius cervicals, but not Masiakasaurus (including anterior cervicals of the latter).

Overall, Thecocoelurus is most similar to Falcarius and least similar to Masiakasaurus.  There are four good characters shared with Falcarius to the exclusion of the Angeac taxon, and three characters that are more similar to Chirostenotes than to the Angeac taxon, but two characters that are more similar to the Angeac taxon than to Chirostenotes.

Thecocoelurus holotype completed with the posterior of Falcarius (modified from Naish and Martill, 2002 and Zanno, 2010).  This results in a centrum length of 68 mm for Thecocoelurus, compared to Naish's (2011) estimate of 70-90 mm.

Falcarius does differ from Thecocoelurus in having a ventral median ridge on its centra, but this is an autapomorphy not seen in other therizinosaurs.  Besides this, no characters differ between the specimen except exact size and shape of pneumatic features, which themselves vary between right and left sides of Thecocoelurus.  Both are Barremian, and Thecocoelurus is 58% the size of the Falcarius individual that preserved the posterior cervical (though a growth series is known, where that individual falls is unreported).  Whether Thecocoelurus and Falcarius share derived characters to the exclusion of other therizinosaurs would require more study, but at the moment is seems most parsimonious to consider Thecocoelurus a basal therizinosaur and not closely related to the Angeac taxon.

References- Sues, 1997. On Chirostenotes, a Late Cretaceous oviraptorosaur (Dinosauria: Theropoda) from Western North America. Journal of Vertebrate Paleontology. 17(4), 698-716.

Naish, Hutt and Martill, 2001. Saurichian dinosaurs 2: Theropods. In Martill and Naish (Eds). Dinosaurs of the Isle of Wight. The Palaeontological Association. 242-309.

Naish and Martill, 2002. A reappraisal of Thecocoelurus daviesi (Dinosauria: Theropoda) from the Early Cretaceous of the Isle of Wight. Proceedings of the Geologists’ Association. 113, 23-30.

Kirkland, Zanno, DeBlieux, Smith and Sampson, 2004. A new, basal-most therizinosauroid (Theropoda: Maniraptora) from Utah demonstrates a Pan-Laurasian distribution for Early Cretaceous therizinosauroids. Journal of Vertebrate Paleontology. 24(3), 25-26.

Lu, 2004. Oviraptorid dinosaurs from Southern China. PhD Thesis. Southern Methodist University. 249 pp.

He, Wang and Zhou, 2008. A new genus and species of caudipterid dinosaur from the Lower Cretaceous Jiufotang Formation of Western Liaoning, China. Vertebrata PalAsiatica. 46(3), 178-189.

Zanno, 2010a. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology. 8(4), 503-543.

Zanno, 2010b. Osteology of Falcarius utahensis: Characterizing the anatomy of basal therizinosaurs. Zoological Journal of the Linnaean Society. 158, 196-230.

Carrano, Loewen and Sertich, 2011. New materials of Masiakasaurus knopfleri Sampson, Carrano, and Forster, 2001, and implications for the morphology of the Noasauridae (Theropoda: Ceratosauria). Smithsonian Contributions to Paleobiology. 95, 53 pp.

Naish, 2011. Theropod dinosaurs. In Batten (ed.). English Wealden Fossils. The Palaeontological Association. 526-559.

Allain, Vullo, Le Loeuff and Tournepiche, 2014. European ornithomimosaurs (Dinosauria, Theropoda): An undetected record. Geologica Acta. 12(2), in press.