Saturday, March 22, 2014

Anzu is no Rosetta Stone (yet?)

Last time I said Aves tests would be my next post, but I didn't know Anzu would be published so soon.  For those out of the loop, Anzu wyliei (Lamanna et al., 2014) is the name given to Triebold's two big Hell Creek caenagnathids, to which are also referred the posterior mandible FMNH PR 2296 (Currie et al.'s 1994 Caenagnathus sp., then catalogued as BHM 2033) and a fragmentary skeleton called Chirostenotes sp. by Schachner et al. (2006).

Caenagnathid taxonomy has been controversial for decades because most species from the Campanian-Maastrichtian are known from parts which don't overlap with others.  Caenagnathus collinsi, C? sternbergi and Leptorhynchos are known from mandibles, Chirostenotes, Hagryphus and Elmisaurus rarus are known from hands, and Macrophalangia, Elmisaurus rarus and E? elegans are known from metatarsi.  In addition, two partial skeletons have been described.  RTMP 79.20.1 preserves a manus and pes but no mandible, and has been agreed by most to be Chirostenotes.  ROM 43250 doesn't preserve mandibles, manus or pes, and has been called Epichirostenotes.  I don't think it differs significantly from Chirostenotes (RTMP 79.20.1 shares the sacrum, ischium and distal tibia), but its later age means it probably was different.  I've been hoping Anzu would be the Rosetta Stone for caenagnathids, since it preserves mandibles, manual material and pedal material, along with sacrum, ischium and tibia.  Alas, at least with the info provided by Lamanna et al., it doesn't seem to help much.

My first inclination was to check the phylogenetic analysis.  The authors did an excellent job sampling basically all oviraptorosaurs and adding characters from the various oviraptorosaur analyses that began back with Maryanska et al. (2002).  Though I do wonder where Protarchaeopteryx is and why the complete Similicaudipteryx specimens weren't coded.  Note the much younger Yulong was included, the poorly illustrated Jiangxisaurus, and the barely codable Ojoraptorsaurus, so none of those seem like reasonable excuses.  It probably explains why Similicaudipteryx ends up in Caudipteridae, since the holotype doesn't preserve the skull or manus.  Also note Lamanna et al. use the incorrect Caudipterygidae instead of Caudipteridae.  In any case, Caenagnathidae is a big polytomy in Lamanna et al.'s strict consensus tree, which is unsurprising if for no other reason than they included Ojoraptorsaurus, a dubious taxon known from an incomplete pubis and only codable for three characters.  The authors then include only caenagnathids known from dentary material and find the same topology as in the Leptorhynchos paper.

But surely Anzu could help us do more?  What about including only caenagnathids known from manual material (Chirostenotes, Elmisaurus, Hagryphus, Anzu)?  Only pelvic material (Chirostenotes, Epichirostenotes, Anzu)?  Only pedal material (Chirostenotes, Macrophalangia, Elmisaurus)?  The authors don't test these, so I did.  And they're all polytomies. I even gave intertaxon overlap its best chance by combining probably synonymous taxa like Longrich et al. (2013), so that collinsi and Macrophalangia are one, Chirostenotes and sternbergi are one, and Elmisaurus/Leptorhynchus is one OTU.  But still, no resolution*.

* The one exception is the pelvic test, where Epichirostenotes is closer to Anzu than Chirostenotes (RTMP 79.20.1).  Alas, this is based on one character, the ventral flange on the pubic peduncle of the ischium, supposedly lacking in the latter.  Going back to the original description of RTMP 79.20.1 by Currie and Russell (1988), they state "The proximal end of the ischium is crushed, so that the iliac and pubic sutures cannot be distinguished" and their figure shows that area with a different texture and irregular outline, suggesting the lack of a flange is taphonomic.  Even if it wasn't, Tyrannosaurus, Microraptor and Archaeopteryx all vary in this character.

Gigantoraptor on the left (after Xu et al., 2007), Anzu on the right (after Lamanna et al., 2014).  Which one is the main postcranial figure from a Nature publication, and which is from a PLoS ONE publication?

So it seems the matrix just doesn't have the characters to distinguish Campanian-Maastrichtian caenagnathids.  But we can compare Anzu to the other taxa ourselves, right?  Well, kinda.  This is my biggest complaint about the paper, namely that illustration- and description-wise, it might as well be in Science or Nature.  The illustrations are gorgeous, don't get me wrong, but there are so few of them.  A total of 20 postcranial elements are illustrated (only 6 in more than one view), out of 31 preserved kinds of appendicular elements and 47 vertebral elements, plus ribs, chevrons and gastralia.  Sure illustrations take time, but what about photographs?  This is PLoS ONE- there's no limit to the number of figures that can be included.  The description is similarly lacking.  This is the first uncontroversial caenagnathid to preserve a scapula, radius, ulna or fibula, but each of these elements gets only one sentence of description and the fibula isn't even illustrated outside the line drawing skeletal reconstruction.  The measurement tables are also only partially complete.  We have the first complete presacral series for a caenagnathid and a tail three-fourths complete, but only three cervicals, two dorsals of unstated position and the three distalmost caudals are measured.  Even the materials list is vague.  The holotype includes "multiple cervical and caudal vertebrae", "several
manual phalanges including unguals" and "several pedal phalanges including unguals", while CMN 78001 includes "several caudal vertebrae" and "several pedal phalanges including unguals".  Why not just be exact?  You can get a bit of this information from the measurement table, but not all of it since only some bones are measured.

All of this combines to make it very difficult to improve caenagnathid taxonomy using Lamanna et al. (2014).  Want to compare the manus to Chirostenotes, Hagryphus and Elmisaurus rarus?  You get three sentences, a drawing of ungual I in one view and measurements of five bones.  Want to compare the sacrum to Chirostenotes and Epichirostenotes?  You get two sentences and three measurements.  Compare the pes to Macrophalangia, Chirostenotes and Elmisaurus?  One sentence, a drawing of an unidentified pedal ungual in one view, and the length of nine bones.  There's just very little to work with, so that the status of Anzu has changed remarkably little with its official publication.  It remains important in theory, but with too little information released to work with much in practice.  Hopefully, this is only a preliminary description that will be supplemented by a monograph in the future.

References- Currie and Russell, 1988. Osteology and relationships of Chirostenotes pergracilis (Saurischia, Theropoda) from the Judith River (Oldman) Formation of Alberta, Canada. Canadian Journal of Earth Sciences. 25, 972-986.

Currie, Godfrey and Nessov, 1994. New caenagnathid (Dinosauria: Theropoda) specimens from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences. 30(10), 2255-2272.

Maryanska, Osmolska and Wolsan, 2002. Avialan status for Oviraptorosauria. Acta Palaeontologica Polonica. 47 (1), 97-116. 

Schachner, Lyson and Hanks, 2006. A preliminary report of a new specimen of Chirostenotes (Oviraptorosauria: Theropoda) from the Hell Creek Formation of North Dakota. Journal of Vertebrate Paleontology. 26, 120A.

Xu, Tan, Wang, Zhao and Tan, 2007. A gigantic bird-like dinosaur from the Late Cretaceous of China. Nature. 844-847.

Lamanna, Sues, Schachner and Lyson, 2014. A new large-bodied oviraptorosaurian theropod dinosaur from the Latest Cretaceous of Western North America. PLoS ONE. 9(3), e92022.

Tuesday, March 11, 2014

Theropod Database info published and credited

I've done my fair share of complaining when material of mine is published without attribution, or ideas suspiciously similar to mine are published.  But there's the flipside as well- when authors credit me in their work, and this post is a thanks to them.

Most recently, Hendrickx and Mateus (2014b) in their description of Torvosaurus gurneyi not only credited me for photos and Dilophosaurus "breedorum" info, they even linked to my blog in the supplementary info.  Thank you so much.

Similarly, Hendrickx and Mateus (2014a) credited me in their theropod tooth paper.  I was very happy to see my hypothesis Richardoestesia is a dromaeosaurid supported by their analysis.

There's also Soto and Perea (2008) on ceratosaurid teeth, Martyniuk (2012) for a lot of things in his field guide as mentioned before, and Zanno and Makovicky (2013) on theropod herbivory.  Thanks everyone.

Coming up... Aves tests.

References- Soto and Perea, 2008. A ceratosaurid (Dinosauria, Theropoda) from the Late Jurassic-Early Cretaceous of Uruguay. Journal of Vertebrate Paleontology. 28(2), 439-444.

Martyniuk, 2012. A Field Guide to Mesozoic Birds and Other Winged Dinosaurs. Vernon, New Jersey. Pan Aves. 189 pp.

Zanno and Makovicky, 2013. No evidence for directional evolution of body mass in herbivorous theropod dinosaurs. Proceedings of the Royal Society B: Biological Sciences. 280(1751), 20122526.

Hendrickx and Mateus, 2014. Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth. Zootaxa. 3759(1), 1-74. 

Hendrickx and Mateus, 2014b.  Torvosaurus gurneyi n. sp., the largest terrestrial predator from Europe, and a proposed terminology of the maxilla anatomy in nonavian theropods. PLoS ONE. 9(3), e88905.

Saturday, March 8, 2014

Testing pterosaur origins in Ezcurra et al. (2014)

There's a new amniote analysis out from Ezcurra et al. (2014) emphasizing the lepidosauromorph-archosauromorph split.  Thev changed a ton of codings from the earlier version by Reisz et al. (2010), almost doubled the size of the matrix, properly ordered most characters, made sure inapplicable codings stopped redundancy in most cases, AND got rid of suprageneric OTUs.  Among the negative points are no parareptiles or aquatic diapsids (yet many synapsids) and a lack of many of the traditional series-based characters (e.g. number of phalanges on digit X, number of vertebrae in this segment).  Regardless, this seems to be better than most amniote analyses, and the lepidosauromorph-archosauromorph split is the perfect place to test pterosaur origins.

Among relevant taxa, the matrix has Peters' closest consensus lepidosaur to pterosaurs, Huehuecuetzpalli, plus two more squamates.  It has Macrocnemus, placed even closer to pterosaurs by him, plus three more protorosaurs.  Also Euparkeria and Erythrosuchus for the Bennett hypothesis.  I added two pterosaurs from the basalmost clade (Preondactylus and Eudimorphodon), Megalancosaurus, Longisquama and Eoraptor.  Note this is far from perfect, as incomplete basal dinosauromorphs (lagerpetonids, Marasuchus), more basal simiosaurs (Vallesaurus, Hypuronector), and more derived pterosaurs with well preserved braincases, palates and axial details would all be useful to add.  Not to mention Scleromochlus, Sharovipteryx, Cosesaurus and Atanassov's taxa.  But what does this preliminary test find?

The pterosaurs were closest to Megalancosaurus, but this clade was sister to Eoraptor within Archosauriformes.  No pseudosuchians were included, so it's uncertain if pterosaurs are strictly archosaurs.  What about Longisquama?  Either a tanystropheid protorosaur or a member of the megalancosaur-pterosaur clade, though note I did (conservatively) use Peters' (2000) illustration for the anatomy.  This may bias it toward those interpretations, though his interpretations were far less fanciful back then.

Forcing pterosaurs to be protorosaurs is 9 more steps, so rather unlikely.  Forcing them to be lepidosauromorphs is 17 more steps though, so probably wrong.

Forcing Megalancosaurus to be an archosauriform outside Ornithodira is only two steps longer, so about equally likely.   The same number of steps move it to Tanystropheidae, with Longisquama following, but not pterosaurs.

Forcing Longisquama to be a lepidosauromorph only takes two steps, and it becomes the most basal one.  Forcing it to be sister to Coelurosauravus results in both being basal lepidosauromorphs, which only takes 3 more steps.  Having this pairing outside Sauria as in Senter (2004) is 5 more steps, so less likely.  Adding Megalancosaurus to complete Senter's Avicephala is 9 more steps though, so rather unlikely.

Finally, enforcing Peters' versions of Lepidosauromorpha (with captorhinids, caseids, weigeltisaurids, trilophosaurs, rhynchosaurs, simiosaurs, Longisquama, tanystropheids and pterosaurs) and Archosauromorpha (with derived synapsids, Paleothyris, araeoscelids and younginiforms) takes a whopping 75 extra steps.  This is worse than any alternative phylogeny I've ever tested for anything.

Instead of asking what pterosaurs are, maybe we should be asking if simiosaurs belong in Archosauria.  Recall even in Nesbitt's (2011) huge analysis focusing on archosaur interrelationships, they could be placed in Avemetatarsalia with only five extra steps.  At the time I thought a broader analysis would be more useful for that question, but here they flit between Archosauriformes and Protorosauria with even less difficulty.  Longisquama is pretty clearly too poorly described to strongly favor any alternative, but it's interesting that Senter's placement for it comes out as badly as it does.  As for what pterosaurs are, while archosauriform beats out protorosaur and both beat out lepidosauromorph, I've seen taxa recover from a 9 step disadvantage often, and a 17 step disadvantage rarely, so both of the latter alternatives are still possible.  75 steps?  Not so much.

References- Senter, 2004. Phylogeny of Drepanosauridae (Reptilia: Diapsida). Journal of Systematic Palaeontology. 2, 257-268.

Reisz, Laurin and Marjanovic, 2010. Apsisaurus witteri from the Lower Permian of Texas: Yet another small varanopid synapsid, not a diapsid. Journal of Vertebrate Paleontology. 30, 1628-1631.

Ezcurra, Scheyer and Butler, 2014. The origin and early evolution of Sauria: Reassessing the Permian saurian fossil record and the timing of the crocodile-lizard divergence. PLoS ONE. 9(2), e89165.

Friday, February 28, 2014

Remember Teyuwasu?

Way back in the days of yore, I had DML post style called "Details on..." where I would report information about obscure dinosaur taxa.  This was before the modern methods of organized file exchange, so to learn more about a newly reported taxon, you'd generally have to request a paper copy from Tracy Ford.  We were all pretty clueless, so I hoped to spread some knowledge around.  One of my posts from 2000 was "Details on Teyuwasu"*, an enigmatic dinosaur described briefly in an abstract and based on  bones first described in an old German paper that was even harder to acquire.  It seems online information on Teyuwasu is still hard to find, so here's an update 14 years later.

* Btw, while I interpreted Kischlat's statement "the distal process is so developed as to encompass the ascending process of astragalus" as being similar to coelophysoids' anterior overlap, it's actually the posterolateral process extending laterally a bit behind the ascending process as in most dinosauriforms.  Hooray for imprecise translations.

Teyuwasu Kischlat, 1999 vide Kischlat, 2000
= "Teyuwasu" Kischlat, 1999
T. barberenai Kischlat, 1999 vide Kischlat, 2000
= "Teyuwasu barberenai" Kischlat, 1999
Late Carnian-Early Norian, Late Triassic
Alemoa Member of Santa Maria Formation, Brazil
Holotype
- (BSPG AS XXV 53) femur (276 mm)
....(BSPG AS XXV 54) tibia (264 mm)
?...(BSPG AS XXV 56-59) dorsal centrum (40 mm), partial ilium, (?) distal ischium, femur
Diagnosis- (proposed) extremely robust femur and tibia (minimum transverse femoral width 19% of length); mound-like fourth trochanter.



A-F: Holotype femur BSPG AS XXV 53 of Teyuwasu barberenai in anterior, medial, posterior, lateral, proximal and distal views respectively. G-L: Holotype tibia BSPG AS XXV 54 in proximal, distal, anterior, medial, posterior and lateral views respectively.  Scale = 100 mm. (after Ezcurra, 2012)

Comments- The material was originally described by Huene (1938) as possibly belonging to his new taxon Hoplitosaurus raui, from slightly higher in the formation. Huene later (1942) renamed it Hoplitosuchus, as Hoplitosaurus was preoccupied by an ankylosaur. The taxon was based on two supposed osteoderms described as aetosaurian, but more recently these have been found to be unidentifiable bones by Kischlat (2000) and Desojo and Rauhut (2008). Kischlat (1999) reinterpreted the femur and tibia as being dinosaurian, though only listed features identifying it to the level of Dinosauriformes. He provided a very brief description and named the taxon Teyuwasu barberenai, but as the publication is a symposium abstract, it is invalid under the ICZN (Article 9.10). Kischlat's (2000) later article has similar information, credits the name to the 1999 paper, but is a valid publication. Ezcurra (2012) described the material in depth, finding it certainly belongs to the silesaurid+dinosaur clade, but that the only dinosaurian character is the inturned femoral head. As the bones have been heavily altered taphonomically, Ezcurra was uncertain if the femoral head orientation was artificial. He notes Kischlat's "two paralell ridges running proximodistally" are fractures formed when the medial femoral head was sheared distally. While Ezcurra declared Teyuwasu to be indeterminate, the robusticty itself is vastly different from other basal dinosauriforms, so should be enough to validate the taxon. If added to the Nesbitt archosaur matrix along with all later published additions (including Nyasasaurus and Saltopus), Teyuwasu emerges as a saurischian based on femur longer or about the same length as the tibia, and medial articular facet of the proximal femur rounded.  It's outside Eusaurischia based on the femoral head being unexpanded, symmetrical fourth trochanter (considered tentative by Ezcurra), cnemial crest not laterally curved, and posterior face of distal tibia without longitudinal ridge.  Some of these characters vary within basal saurischians, which are incompletely sampled by Nesbitt, so I wouldn't bet on a non-eusaurischian identity being most parsinomious once all data are in.  Additionally, the coding indicates the moundlike fourth trochanter is unique among sampled ornithodirans, making this another diagnostic character.

Besides the femur and tibia, Huene referred additional material to this individual. A centrum identified by Kischlat (2000) as dorsal was stated by Huene to be possibly but not certainly referrable to this specimen. It is 40 mm long, 45 mm tall and wide, rounded in section and barely amphicoelous to amphiplatyan. A ventral ilium was considered very likely to belong to this individual. It has a supracetabular crest and 'strongly recessed' acetabulum, and narrows to 70 mm between the peduncles and blade. An element tentatively identified by Huene as a distal ischium is much too large to belong to this individual, with the distal end 90 mm deep and 60 mm wide. At the proximal break, these dimensions are 53 and 30 mm respectively. The distal end is triangular in section, which is a saurischian character. Finally, Kischlat (2000) mentioned an additional femur which was not noted by Huene. These were all noted by Kischlat as supplementary material for Teyuwasu, though Desojo and Rauhut stated referred Hoplitosuchus material belongs to Rauisuchia and Dinosauria. The centrum, ilium and/or ischium may comprise the 'rauisuchian' material, or this may refer to the two non-avemetatarsalian calcanea also referred to Hoplitosuchus by Huene.

References- Huene, 1938. Ein grosser Stagonolepid aus der jungeren Trias Ostafrikas. Neues Jahrbuch fur Mineralogie, Geologie und Palaontologie. 80(2), 264-278.

Huene, 1942. Die fossilen Reptilien des sudamerikanischen Gondwanalandes. Ergebnisse der Sauriergrabungen in Sudbrasilien 1928/29. Munich: Becksche Verlegbuchhandlung. 332 pp.

Kischlat, 1999. A new dinosaurian "rescued" from the Brazilian Triassic: Teyuwasu barbarenai, new taxon. Paleontologia em Destaque, Boletim Informativo da Sociedade Brasileira de Paleontologia. 14(26), 58.

Kischlat, 2000. Tecodoncios: A aurora dos Arcosaurios no Triassico. in Holz and De Rose (eds.). Paleontologia do Rio Grande do Sol. 273-316.

Desojo and Rauhut, 2008. New insights on "rauisuchian" taxa (Archosauria: Crurotarsi) from Brazil. SVPCA 2008 Programme and Abstracts. 18-19.

Ezcurra, 2012. Comments on the taxonomic diversity and paleobiogeography of the earliest known dinosaur assemblages (Late Carnian-Earliest Norian). Historia Natural. 2(1), 49-71.

Saturday, February 22, 2014

What is Eoraptor revisited 1 - Outside Eusaurischia?

You all know the big Eoraptor monograph was finally published as Sereno et al. (2013) containing the first detailed description of the material.  It may have taken 22(!) years from discovery to publication, but it's an excellent paper.  I previously examined the evidence Martinez et al. (2011) provided for Eoraptor being a sauropodomorph when they announced the idea in their Eodromaeus paper.  I found numerous coding issues and errors, such as composite codings and miscodings, which when partially corrected recovered a theropod Eoraptor instead, and also noted few of the proposed theropod characters had been included in their matrix.

Since then, we have the new basal theropod Daemonosaurus, redescriptions of basal sauropodomorphs Chromogisaurus and Pantydraco, redescriptions of all heterodontosaurids, redescriptions of the near/basal-dinosaurs Saltopus and Nyasasaurus, a version of Yates' analysis finding Eoraptor to be a sauropodomorph and more characters from Nesbitt's and Ezcurra's analyses finding it to be a theropod closer to Avepoda than herrerasaurids.  So let's explore the suggested evidence for each position for Eoraptor.  I'll list all novel suggested characters from each analysis, bolding the ones that seem valid.

Outside Eusaurischia (Sauropodomorpha+Theropoda)

 Padian et al. (1999)
1. centra of posterior cervical vertebrae (6-8) subequal in length to those of anterior dorsal vertebrae (refined by Langer, 2004).  This is untrue in Eoraptor, as cervicals 6-8 are 18-23 mm and the anterior dorsals are 16-17 mm.
2. third finger of the manus longer than second finger.  As this is true in Eodromaeus and Tawa, the opposite condition in known sauropodomorphs and avepods is probably convergent.  Herrerasaurus  also has III longer than II, while Guaibasaurus is like sauropodomorphs and avepods.  Though Tianyulong has an avepod-like condition, Heterodontosaurus and derived ornithischians have III longest, so this was more likely the basal condition in Ornithischia.
3. metatarsal I contacts tarsus.  Since this is also true in Sauropodomorpha, the authors had no reason to list it.  It only excludes Eoraptor from Avepoda.

Langer (2004)
4. subnarial premaxillary process extends posteriorly to the external naris.  This is also true in Daemonosaurus, making the basal condition for Theropoda ambiguous.  As Herrerasaurus has this state as well, it's even worse if herrerasaurids are theropods.
5. radius more than 80% of humerus length.  This is untrue in Eoraptor, which has a ratio of 74%.
6. manual ungual I shorter than metacarpal I.  This is untrue in Eoraptor, which has a ratio of 100%.  Note even if the ratio is actually barely in agreement, Eodromaeus and Tawa have short unguals I too, so it would be another character convergent in avepods and sauropodomorphs.
7. metacarpal III longer than metacarpal II.  Another character also present in Eodromaeus and Tawa, again making sauropodomorphs and avepods convergent. As with the digit length comparison, Guaibasaurus has longer II while Herrerasaurus has longer III.  Also while heterodontosaurids have longer II, other ornithischians and Saltopus have longer III, suggesting the former is convergence.
8. distal end of ischium unexpanded. This is untrue in Eoraptor.
9. medial margin of distal tibia not broader than lateral margin. This is untrue in Eoraptor.

Smith et al. (2007)
10. maxillary tooth count 12-18. Eoraptor has 17, while basal theropods have (9/10)-11 and basal sauropodomorphs don't preserve the area or have unreported counts.  As Saturnalia and Panphagia have 17 and 23 dentary teeth respectively, their maxillary counts were probably within the 12-18 range or higher, not lower as in basal theropods. Thus there is no shared derived state to differ from.
EDIT: Ugh, how could I forget Pampadromaeus?!  It has at least twenty maxillary teeth, proving my point.
11. lateral surface of anterior end of nasal along the posterior margin of the external naris flat.  Pantydraco and Daemonosaurus also lack this narial fossa, though Panphagia has it.  This means Theropoda is basally ambiguous while Sauropodomorpha is barely basally derived in having the fossa, so the character is not an unambiguous eusaurischian synapomorphy.  For what it's worth, Herrerasaurus also lacks the fossa.
12. posteroventral dentary process far posterior to posterodorsal process.  This is true in basal sauropodomorphs  (Panphagia, Pantydraco) and basal theropods (Eodromaeus, Tawa).  It's not true in ornithischians (Tianyulong, Heterodontosaurus, Eocursor) though, making the condition in Saurischia's outgroup ambiguous (given Silesaurus having the opposite condition).  Again for what it's worth, Herrerasaurus has the same condition as ornithischians.
13. foramen in the ventral part of the splenial absent.  This is difficult to code as the anterior splenial is thin and often broken.  In Sauropodomorpha, Panphagia has a foramen, Lamplughsaura is illustrated without one (though by Chatterjee, whose drawings are often idealized), Plateosaurus is polymorphic, and Lufengosaurus and Adeopapposaurus have it.  In Theropoda, Liliensternus lacks one, Dilophosaurus is illustrated as lacking one but seems to be anteriorly incomplete, and Ceratosaurus has one.  Thus the basal condition in either saurischian clade is unclear though more probably present in sauropodomorphs.  Ornithischians lack the foramen, as does Staurikosaurus though the latter has a poorly preserved mandible.
14. iliac supraacetabular crest shelf-like and short, extending primarily laterally.  This is also true in basal sauropodmorphs (Panphagia, Pampadromaeus) and basal theropods (Eodromaeus, Tawa).
15. ridge on lateral side of tibia for connection with fibula absent. This is untrue in Eoraptor

Yates (2007)
16. relationship between posterolateral process of the premaxilla and the anteroventral process of the nasal a broad sutured contact.  This is untrue in Eoraptor.
17. size and position of subnarial foramen small (no larger than adjacent maxillary neurovascular foramina) and positioned outside of narial fossa.  Basal theropods (Tawa, coelophysids, Dilophosaurus) lack a subnarial foramen, as do outgroups (ornithischians, Silesaurus).  Thus there is no obvious ancestral condition for the subnarial foramen, nor evidence theropods ancestrally had one.  Herrerasaurus does have this condition.
18. pointed posterolateral process of the nasal overlapping the lacrimal absent. This is untrue in Eoraptor.
19. length of middle to posterior cervical centra (6-8) no more than the length of the axial centrum. This is unknown in Eoraptor, as the axis is fragmentary.
20. laminae bounding triangular infradiapophyseal fossae on dorsal neural arches absent. This is untrue in Eoraptor.
21. transverse width of the first distal carpal less than 120% of the transverse width of the second distal carpal. This is unknown or untrue in Eoraptor, as distal carpal I is either unpreserved or diagenetically fused to the radiale in the left carpus and ~192% the width of distal carpal II. Notably, the basal theropods Eodromaeus and Tawa and basal sauropodomorph Efraasia have a small distal carpal I though, so this is not a eusaurischian character, though Heterodontosaurus does have a large distal carpal I so that ornithischians have an ambiguous basal state. Herrerasaurus has a small distal carpal I.

Martinez and Alcober (2009)
22. no caudosacral.  This is also true in basal theropods (Eodromaeus and Tawa) and ambiguous in sauropodomorphs (true in Pampadromaeus but not Efraasia and more derived taxa).  Guaibasaurus, Sanjuansaurus and Herrerasaurus also lack a caudosacral, though Staurikosaurus may have one.  Ornithischians have a caudosacral.
23. width of metacarpal I shaft less than 35% of length. This is untrue in Eoraptor.

Bittencourt Rodrigues (2010) also placed Eoraptor basal to Eusaurischia, but this paper has yet to be translated.

What's that?  No characters were bolded?  These turned out particularly bad, with almost half (10-11) not even being present in Eoraptor.  The others are basically all also found in taxa agreed to be basal theropods (11) and/or sauropodomorphs (7).  The best character is the absent anterior splenial foramen, which depends on illustration inaccuracy of a poorly preserved and seldomly exposed element.

Next up- is it a sauropodomorph?

References- Padian, Hutchinson and Holtz, 1999. Phylogenetic definitions and nomenclature of the major taxonomic categories of the carnivorous dinosaurs Dinosauria (Theropoda). Journal of Vertebrate Paleontology. 19(1), 69-80.

Langer, 2004. Basal Saurischia. In Weishampel, Dodson and Osmolska. The Dinosauria Second Edition. University of California Press. 861 pp.

Smith, Makovicky, Hammer and Currie, 2007. Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution. Zoological Journal of the Linnean Society. 151, 377-421.

Yates, 2007. Solving a dinosaurian puzzle: The identity of Aliwalia rex Galton. Historical Biology. 19(1), 93-123.

Martinez and Alcober, 2009. A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha. PLoS ONE. 4(2), e4397.

Bittencourt Rodrigues, 2010. Revisao filogenetica dos dinossauriformes basais: Implicacoes para a origem dod dinossauros. Unpublished Doctoral Thesis. Universidade de Sao Paulo. 288 pp.

Martinez, Sereno, Alcober, Columbi, Renne, Montanez and Currie, 2011. A basal dinosaur from the dawn of the dinosaur era in Southwestern Pangaea. Science. 331, 206-210.

Sereno, Martinez and Alcober, 2013. Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology. 32(Supplement to 6), 83-179.

Monday, February 17, 2014

Zhongornis probably isn't scansoriopterygid, contra O'Connor and Sullivan (2014)

Hi everyone.  Today we're looking at O'Connor and Sullivan's (2014) paper reinterpreting Zhongornis.  As the abstract says "The recently described maniraptoran theropod Zhongornis haoae, known from a single juvenile specimen, was originally identified as a bird. However, morphological re-evaluation reveals striking resemblances to both Oviraptorosauria and Scansoriopterygidae."  Well, does it?

No.

This is one of those papers that got worse and worse as I read more of it.  It seems to be written to reach a certain conclusion, but finds a different conclusion that is basically unacknowledged.  There are only a few actual reinterpretations of anatomy, namely the sacrum as having less vertebrae (5-6 instead of 6-7), the tail as having more vertebrae (~20 instead of 13-14), a less elongate coracoid and an ischium without a proximodorsal process (reinterpreted as the ilial peduncle).  Are these better than Gao et al.'s (2008) original interpretations?  It's impossible to tell, since the figures are terribly compressed jpegs that show artifacts even in the line drawings.  I've requested better versions from O'Connor but have yet to receive a reply.  Regardless, let's look at the evidence Zhongornis is closely related to scansoriopterygids and/or oviraptorosaurs.

The stated similarities to scansoriopterygids are as follows-

1. Short and deep skull.  Expected in any juvenile.
2. Short humerus (humerofemoral ratio 104% compared to scansoriopterygids' 98-112%).  Also expected in younger specimens, and a similar distance from adult Confuciusornis (114-127%) as the juvenile Liaoxiornis (108%) is from the adult Cathayornis (117%).
3. Weakly curved manual unguals with low flexor tubercles.  The curvature is actually similar to confuciusornithids and other basal birds.  O'Connor and Sullivan have a simplistic idea of basal birds and deinonychosaurs having more strongly curved manual unguals than oviraptorosaurs or scansoriopterygids, but there is a lot of variation in each. Also Scansoriopteryx and Epidexipteryx actually have large flexor tubercles.
4. Reduced number of caudal vertebrae (~20).  This is only true in Epidexipteryx (16) and admitted to be absent in Scansoriopteryx (~30-35).  This is also true in pygostylians of course (e.g. juvenile Dalingheornis with unfused caudals has ~20).
5. No distinct transition point or elongated distal caudals.  This is untrue in scansoriopterygids, where the distal vertebrae are elongate with reduced neural spines and transverse processes.  It can't really be evaluated in pygostylians with a pygostyle, though juveniles lacking a pygostyle like Dalingheornis are similar to Zhongornis and Epidexipteryx.
6. 'Incipient' pygostyle.  This phrase is used incessantly throughout this paper, but is never defined sufficiently.  The distal caudals in Zhongornis and Epidexipteryx are unfused (Scansoriopteryx's are unpreserved), so are not strictly pygostyles.  O'Connor and Sullivan cite Persons et al. (in  press) as attributing an incipient pygostyle to Caudipteryx, because "the last five vertebrae appear to be tightly integrated into an inflexible unit." But this is true of any coelurosaur, as the last caudals generally have flat articular surfaces and often elongate zygapophyses. Any pygostyle development is at least as true in pygostylians as it is in Epidexipteryx.
7. No obturator process.  Also true in Pygostylia, Jeholornithidae and Omnivoropterygidae.
8. Penultimate pedal phalanges longest.  This is not true in Scansoriopteryx, which has III-3 equal to III-1 and IV-4 equal to IV-1.  It is unpreserved in Epidexipteryx.  II-2 is longer than II-1 in most basal avialans as well, including confuciusornithids.
9. Manual phalanx I-1 longer than metacarpal II.  This is untrue in Zhongornis (94%) and scansoriopterygids (91% in Scansoriopteryx), and is similar to basal avialans (91% in Balaur; ~92% in Confuciusornis) and basal oviraptorosaurs (~93% in Similicaudipteryx; 89-93% in Caudipteryx).
10. Lack of proximodorsal ischial process.  This would be similar to scansoriopterygids, but the poor preservation proximally and great simiarity in shape to taxa with such processes (e.g. juvenile enantiornithine GMV-2158) make this equivocal at least.

Left ischia in lateral view of Zhongornis (top; after O'Connor and Sullivan, 2014), juvenile enantiornithine GMV-2158 (middle; after Chiappe et al., 2007), Scansoriopteryx holotype (bottom ; after Czerkas and Yuan, 2002).  Note the similarity between Zhongornis and GMV-2158, suggesting the process on the upper right is the proximodorsal process and not the iliac peduncle.
So we have no good scansoriopterygid characters in Zhongornis

How about oviraptorosaurian ones?

1. Low number of sacrals.  This could easily be ontogenetic, as juveniles often have less sacral vertebrae than adults.  The enantiornithine GMV-2158 has six sacrals for instance, when adult enantiornithines have seven or eight.  So if O'Connor and Sullivan are right that Zhongornis has 5-6, that would work if the adult had seven sacrals like confuciusornithids.
2. 'Incipient' pygostyle.  The argument used above works here- incipiency is a vague descriptor and any pygostyles are present in pygostylians as well.
3. Concave anterior narial margin formed by premaxilla.  This is true in the vast majority of theropods, pygostylians included.
4. Long frontals.  This is a confusing character to list here, since oviraptorosaurs usually have shorter frontals than most coelurosaurs due to their longer parietals.  Thus frontal length doesn't provide evidence Zhongornis is an oviraptorosaur.
5. Frontals narrow anteriorly and greatly expanded posteriorly.  Another confusing character, since oviraptorosaurs generally have less triangular frontals than most coelurosaurs.
6. Short and robust tail.  The tail is about equally short in juvenile pygostylians (e.g. length 1.59 times femoral length in Dalingheornis), Zhongornis (1.54) and basal oviraptorosaurs (~1.5 in Caudipteryx, 1.36 in Similicaudipteryx).  Oviraptorosaurs' tails are robust due to long chevrons (unpreserved in Zhongornis) and transverse processes (short in Zhongornis).  Thus there is no evidence Zhongornis has a tail that is robust for its length.
7. Robust furcula.  Basal oviraptorosaurs like Protarchaeopteryx, Similicaudipteryx and Caudipteryx actually have gracile furculae, and basal avialans like confuciusornithids have robust furculae.
8. Pointed epicleidia on furcula.  This is similar to some oviraptorids (Oviraptor, Citipati), though lacking in others (Khaan, Conchoraptor, "Ingenia", Jiangxisaurus, Heyuannia).  Unfortunately, other oviraptorosaurs do not preserve epicleidia in anterior/posterior view.
9. Metacarpal I 33% of metacarpal II length.  While shorter in many basal avialans, this is even stated by the authors to be present in Confuciusornis, and is even longer in Changchengornis and Balaur.  
10. Metacarpal I wider than metacarpal II.  Again, this is present in confuciusornithids and Balaur.
11. Manual phalanx I-1 subequal in length to metacarpal II.  As discussed in scansoriopterygid-like character 9 above, this is similar in Zhongornis, Confuciusornis and Balaur.
12. Weakly curved manual unguals.  As noted above, there is a lot of variation in oviraptorosaurs, with e.g. Protarchaeopteryx having more strongly curved unguals than Caudipteryx.  The curvature in Zhongornis isn't more similar to oviraptorosaurs' than pygostylians'.
13. Long nasals.  Another confusing character, since oviraptorosaurs have shorter nasals than most coelurosaurs.
13. ~20 caudal vertebrae.  This is not different from basal pygostylians as e.g. the juvenile Dalingheornis holotype has about 20 caudal vertebrae while lacking a pygostyle.
14. Reduced manual digit III of three phalanges. This may not be true (a short III-1 may be hidden), but the similarity to Caudipteryx's two phalanges noted by O'Connor and Sullivan is problematic for two reasons. First, as they state, Sapeornis has less than four phalanges on digit III (also true in Balaur). More importantly, the authors are not proposing a caudipterid identification for Zhongornis, and more basal oviraptorosaurs like Protarchaeopteryx and Similicaudipteryx have an unreduced digit III.

Only the narrowly pointed epicleidia are more similar to some oviraptorosaurs than to basal pygostylians.  O'Connor and Sullivan go on to compare scansoriopterygids with oviraptorosaurs, listing supposedly shared characters, and stating "We suggest that accumulating morphological information regarding both scansoriopterygids and basal oviraptorosaurs may eventually demonstrate that the former clade is either on the oviraptorosaurian stem or nested within basal Oviraptorosauria (Fig. 3), and convergently evolved ‘avian characteristics’ as a result of adaptation to an arboreal lifestyle."

Analysis and unjustified conclusions

Of course just listing characters isn't that useful, and O'Connor and Sullivan proceed to add Zhongornis to the Xiaotingia version of Senter's TWG matrix.  They recover it as the most basal avialan, followed by Scansoriopterygidae, Jeholornis and Avebrevicauda.  Deinonychosaurs (including archaeopterygids) are sister to Avialae, with oviraptorosaurs and therizinosaurs more basal.  So hypotheses unsupported, right?  You'd think so, but the authors go on as if the opposite had occured.

Strict consensus tree of O'Connor and Sullivan (2014).  Note Aves should either be within Ornithuromorpha or at the Paraves node, depending on the definition used.  Is it suspicious the Paraves clades are flipped so that Zhongornis and scansoriopterygids are next to oviraptorosaurs?
 "Scansoriopterygidae is recovered as the sister taxon to Aves, with the two together forming the clade Avialae."

Since when is Jeholornis+Avebrevicauda Aves?  Aves is either crown birds, or Archaeopteryx plus crown birds, which would be Eumaniraptora here.

"Zhongornis is resolved as sister taxon to Avialae (Scansoriopterygidae + Aves) supporting our hypothesis that Zhongornis is closely related to scansoriopterygids."

First, the scansoriopterygid+jeholornithid+avebrevicaudan clade doesn't correspond to any proposed definition of Avialae.  Either Zhongornis is an avialan because it's closer to Aves than dromaeosaurids and/or troodontids (Gauthier, 1986), because it has wings for powered flight homologous to Aves (Gauthier and de Queiroz, 2001) (moreso than scansoriopterygids seem to at least) or because it's in the Archaeopteryx+Aves clade (Gauthier and Wagner, 2001).
Second, it's only closely related in the Petersian sense of being sister to a clade including scansoriopterygids and another branch.  You could just as validly say Zhongornis is closely related to Jeholornis+avebrevicaudans.

"A relationship between Zhongornis and Scansoriopterygidae is supported by six characters (101, 103, 166, 273, 317, and 325); however, scorings for most of these characters are ambiguous in Zhongornis because of missing data. The only one whose presence can be confirmed in Zhongornis, namely the fact that the minor digit is shorter than the major digit, is absent in Epidendrosaurus."

Er.... a relationship can't be supported by characters that are unknown in one of the two taxa.   Having a supporting character lacking in one taxon is even less sensical.  Obviously character 325 (manual digit III longer than II) can't support this clade if it is absent in Zhongornis.  I'm honestly not sure what this list is supposed to be.  I'd say it's a list of Avialae characters in ACCTRAN (where traits are optimized as evolving as early as possible, so that the basalmost avialan Zhongornis is modeled as having characters unknown for it but present in more derived birds), except 325 should just be a scansoriopterygid character and the actual list of avialan characters should include e.g. obturator process absent.  Alas, O'Connor and Zhou don't include their matrix, so we can't know for now.

We get numerous proclamations such as-
"This study reveals new morphological information that strongly suggests the holotype of Zhongornis is a juvenile scansoriopterygid or close scansoriopterygid relative."
"Based on new morphological data and comparisons with other avian and non-avian taxa, we suggest that the Early Cretaceous ‘bird’ Zhongornis haoae may in fact be either a member or a close relative of the Scansoriopterygidae"
"Revised anatomical interpretation of the tail and more detailed comparisons with non-avian dinosaurs strongly suggest that Zhongornis haoae is not a bird but a member or close relative of the enigmatic maniraptoran clade Scansoriopterygidae."

The analysis didn't even suggest Zhongornis is a scansoriopterygid, let alone strongly suggest it.  Again the authors ignore the equally strong suggestion from their analysis that Zhongornis is a close relative of more derived avialans.

"The apparent scansoriopterygid affinities of Zhongornis would suggest the clade persisted from the Mid-Late Jurassic Daohugou times into Early Cretaceous Jehol times."

Whoah whoah... now the placement of Zhongornis in Scansoriopterygidae is apparent?  

"Zhongornis also bears some similarity to basal oviraptorosaurs, supporting the hypothesis that the Jurassic scansoriopterygids may be stem-group relatives of the Cretaceous Oviraptorosauria."

Apparently it didn't, since scansoriopterygids are avialans in their tree, while oviraptorosaurs are further removed than deinonychosaurs.  And I'm sure Mike Keesey is wondering what the crown-group oviraptorosaurs are. ;)
And tying both MIA hypotheses together...

"The relatively short forelimbs and short hallux in Zhongornis may suggest this taxon is a basal scansoriopterygid, close to the divergence of this clade from basal oviraptorosaurs, although this is inconsistent with its occurrence in the Yixian."

Well, IF Zhongornis were a scansoriopterygid and IF scansoriopterygids were oviraptorosaurs, that might be true.  Though Zhongornis actually has longer forelimbs (84% of hindlimb length, excluding phalanges) than scansoriopterygids (70-81%), and an equally long hallux (I-1 23% of metatarsal II).  So even this doubly hypothetical scenario then doesn't match with the evidence.

Sadly, this paper reminds me most of something from Feduccia or Martin.  O'Connor and Sullivan start with a relationship in mind and list characters to support it, but these are generally incorrect or equally correct for the opposing hypothesis.  They also often compare characters to different taxa in a group, so Zhongornis is like oviraptorids but not Caudipteryx in A and B, and like Caudipteryx but not oviraptorids in X and Y, so therefore is like oviraptorosaurs.  Phylogenetic terms are misapplied, and the result of any analysis is only important in the ways that it agrees with their ideas, not in the ways it disagrees.  One gets the impression the original draft never even included an analysis, as the discussion doesn't take it into account and the authors seem not to know how to evaluate their ideas with that dataset.  What they should have done is constrain scansoriopterygid and oviraptorosaurian Zhongornis to see how unparsimonious those hypotheses are, then constrain oviraptorosaurian scansoriopterygids including or excluding Zhongornis.  I've done that in the Lori analysis, and will say the results are much closer to their cladogram than their written ideas.

References- Czerkas and Yuan, 2002. An arboreal maniraptoran from Northeast China. Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum Journal. 1, 63-95.

Chiappe, Ji ans Ji, 2007. Juvenile birds from the Early Cretaceous of China: Implications for enantiornithine ontogeny. American Museum Novitates. 3594, 46 pp.

Gao, Chiappe, Meng, O'Conner, Wang, Cheng and Liu, 2008. A new basal lineage of Early Cretaceous birds from China and its implications on the evolution of the avian tail. Palaeontology. 51(4), 775-791.

O'Connor and Sullivan, 2014. Reinterpretation of the Early Cretaceous maniraptoran (Dinosauria: Theropoda) Zhongornis haoae as a scansoriopterygid-like non-avian, and morphological resemblances between scansoriopterygids and basal oviraptorosaurs. Vertebrata PalAsiatica. 52(1), 3-30. 

Persons, Currie and Norell, in press. Oviraptorosaur tail forms and functions. Acta Palaeontologica Polonica. doi: http://dx.doi.org/10.4202/app.2012.0093

Friday, January 31, 2014

Vitakridrinda the croc and croc phylogeny

Hi everyone.  With Lori "done", let's try to get more blog posts up this year.  First is something Molnar told me about last year and gave me permission to discuss since he wasn't going to write it up.  So I wrote about it in the Database in September, then forgot to mention it once I uploaded the revised pages on New Years.  Without further ado...

Figure 1. Comparison between Vitakridrinda syntype snout MSM-155-19 (top; from Malkani, 2010) and Pabwehshi holotype snout GSP-UM 2000 (bottom; from Wilson et al., 2001).  Both in sagittal section.

Vitakridrinda's syntype snout (originally described as abelisaurian by Malkani) is a really good match for the baurusuchid crocodyliform PabwehshiPabwehshi is from the same formation and about 50% larger, though the latter measurement will vary based on how far down the snout each cross section is. The nasal diverticulum seen in Vitakridrinda is listed by Wilson et al. (2001) as an autapomorphy of Pabwehshi, but the internal anatomy of other baurusuchid snouts is poorly known, though Baurusuchus, Stratiotosuchus and Wargosuchus at least lack evidence of it in the external naris. Under Molnar's interpretation, Malkani's dorsal palatal process (dpp above) is the secondary palate, the ventral palatal process (vpp) is the mandible, the cavity between these is the oral cavity, and the cavity in the ventral palatal process is the Meckelian canal. This leaves almost all of Malkani's supposed lateral surface as matrix which needs to be prepared to expose bone. Thus his supposed bite punctures are merely grooves excavated in the matrix, while his 'combat teeth' are tooth cross sections ventral to the dentary. Malkani's scenario of intraspecific combat causing these features is thus exposed as being fanciful. While most features of Vitakridrinda's snout as described by Malkani are based on misinterpretation, it should be noted Pabwehshi has labiolingually compressed tooth crowns with mesial and distal serrations and a more convex mesial edge as in abelisaurids.

I think this is a really good observation, and have since learned that Molnar heard it from Wilson, one of Pabwehshi's coauthors.  In November, Malkani himself independently contacted me for advice with manuscripts, one of which also uses Wilson's suggestion.  He came to different taxonomic conclusions than I did, but agrees on the basic point of the snout being from a croc, which further strengthens the idea.

This of course leads to the question of what the rest of the Vitakridrinda type material belongs to.  The limb bone (femur?) segments (MSM-59-19, 60-19) are possibly theropod due to their supposed inturned head, distinct neck, and hollowness, though Malkani (2009) states a section "has fibrous bone network in the hollow", so perhaps they are not actually hollow. The stated lack of an anterior trochanter may support a crocodiliform identity, or may be due to preservation. The supposed braincase (MSM-61-19) matches Baurusuchus as poorly and ambiguously as it does abelisaurids, so remains an unidentified object. The supposed tooth cross section (MSM-62-19) works as well for Pabwehshi as it does for abelisaurids.  So the basic answer is that the published data is too crummy to tell.  This is unfortunate because exactly what specimen the name Vitakridrinda should be connected to is uncertain.  Malkani refers to all of the type material as the holotype, as he thought they all belonged to one individual.  Since the ?braincase and ?femora were found 100 meters away from each other, this seems unlikely, and one (or the snout) should really be selected as a lectotype.  Malkani's manuscript will clarify some of this if it is published, but I fear without further preparation and better photography, Vitakridrinda's possible synonymy with Pabwehshi and syntypic identification will remain uncertain.

What is Pabwehshi?

Finally, because it's me, some phylogenetic tests!  I thought it would be simple to just add Vitakridrinda/Pabwehshi to the baurusuchid part of my croc tree, but then saw a more recent paper (Montefeltro et al., 2011) examining baurusuchid phylogeny excluded it from the family.  Those authors referenced another paper (Larsson and Sues, 2007; top tree in figure 2) that found it sister to a clade of sebecids and peirosaurids instead.  They named this clade Sebecia, and noted similarity between Pabwehshi and the peirosaurid Hamadasuchus in particular, which had not been included in prior analyses that found Pabwehshi to be a baurusuchid.  And so I had to enter the confusing and conflicting world of croc phylogeny.

What I found was interesting.  First, Larsson and Sues excluded Pabwehshi a priori because "it has a sagittal torus on its maxillary palatal shelves, absent in the putative baurusuchids".  So they didn't test it themselves, and indeed if added to their matrix, Pabwehshi comes out sister to other baurusuchids.  Second, adding Hamadasuchus to those earlier analyses that placed Pabwehshi in Baurusuchidae does make Sebecia more likely than before (by 1-4 steps), though it is still unparsimonious.  Sebecia takes 8 extra steps to enforce in these early analyses.  But in none of those cases does Pabwehshi move to Sebecia, needing 1-4 additional steps to go there once Sebecia is enforced.  As analyses get larger and more recent, it takes increasing numbers of extra steps to move it, and it's always closer to sebecids than to Hamadasuchus.

Figure 2. Comparison of Larsson and Sues' (2007) topology at top to Pol et al.'s (2012) below.  Note the top one has orange sebecids sister to green peirosaurids to make Sebecia, while the bottom one based on a much larger analysis has sebecids sister to red baurusuchids instead.  They also differ in that the top one has blue neosuchians sister to Sebecia, whereas sebecians are interspersed throughout the other taxa in the bottom one to form a huge Notosuchia to leave neosuchians basal instead.  Red Pahwehshi is a sebecian on top, but a baurusuchid on bottom.

The most recent analysis (Pol et al., 2012; bottom tree in figure 2) is much larger (347 characters, 88 taxa) than Larsson and Sues' (158 characters, 33 taxa) and includes a ton more postcranial characters, and postcranial codings for taxa like Baurusuchus, Sebecus, Notosuchus and Araripesuchus that were not coded postcranially by Larsson and Sues due to a lack of material/description.  It takes 4 extra steps to move Pabwehshi to Sebecia if the latter is forced to exist, and again is close to sebecids in that case.  Forcing Sebecia to exist in the first place though only takes 5 extra steps, which isn't too bad.  However, it ends up in that uruguaysuchid+pierosaurid clade which is sister to other notosuchians.  To get it to be sister to the blue neosuchians like in Larsson and Sues' tree takes 16 more steps, so seems unlikely.  As Pol et al. describe in their paper, this is due to all of the new characters and codings for Sebecus et al.'s postcrania, so while Sebecia itself isn't dead, Larsson and Sues' placement for it may be.

Importantly, even when Sebecia is enforced, Pabwehshi still clades with baurusuchids and most analyses (including the largest ones) take 4 extra steps to move it into Sebecia. This suggests there is no sebecian signal in Pabwehshi, as does the lack of a particular position within Sebecia when it is forced to be there (sister to either Bretesuchus, Iberosuchus, or a wildcard basal sebecid). Notably it is always attracted to sebecids though, which are sister to baurusuchids in non-sebecian phylogenies, as opposed to being isolated or close to Hamadasuchus as in Larsson and Sues' paper. While Hamadasuchus is important for making Sebecia itself more likely (by 1-6 extra steps), it only made Pabwehshi more likely to be a sebecian in one analysis, and then only by one step.

And there ends our foray into croc phylogeny.  See more detail on the material and analyses at the Database entry.  I'd love to add more taxa to Pol et al.'s analysis, like the large number of notosuchians that were left out, and the newly redescribed Shartegosuchidae that seems to be basal to Neosuchia+Notosuchia, so are probably important for settling the basal relationships of those clades.  But there's only so much time, and based on the rampant miscodings and poorly defined characters in theropod analyses, I'm not confident croc analyses are any better.  Which means checking matrices, which means acquiring literature past my current 372 croc pdfs, which means lots of work, so next time it's back to theropods.

References- Wilson, Malkani and Gingerich, 2001. New crocodyliform (Reptilia, Mesoeucrocodylia) from the Upper Cretaceous Pab Formation of Vitakri, Balochistan (Pakistan). Contributions from the Museum of Paleontology. The University of Michigan. 30(12), 321-336.

Larsson and Sues, 2007. Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco. Zoological Journal of the Linnean Society. 149, 533-567.

Malkani, 2009. New Balochisaurus (Balochisauridae, Titanosauria, Sauropoda) and Vitakridrinda (Theropoda) remains from Pakistan. Sindh University Research Journal (Science Series). 41(2), 65-92. 

Montefeltro, Larsson and Langer, 2011. A new baurusuchid (Crocodyliformes, Mesoeucrocodylia) from the Late Cretaceous of Brazil and the phylogeny of Baurusuchidae. PLoS ONE. 6, e21916.

Pol, Leardi, Lecuone and Krause, 2012. Postcranial anatomy of Sebecus icaeorhinus (Crocodyliformes, Sebecidae) from the Eocene of Patagonia. Journal of Vertebrate Paleontology. 32, 328-354.