Monday, October 19, 2015

SVP 2015 Day 4

The final day.  Let's see what happened...

In another ornithischian abstract, Borinder et al. redescribe the hadrosaur Tanius.  As the authors state, it's been 86 years since the genus was described.  The only known specimen is immature and has a flexor canal on the femur.  Unfortunately, it emerges in a big polytomy with other taxa just outside Hadrosauridae.  I do wonder if excluding some of these nine taxa a posteriori might show some resolution between the remaining ones and Tanius.

Cranial elements of Tanius sinensis holotype (after Wiman, 1929).

Cuesta et al. argue that the ulnar bumps of Concavenator are homologous to the secondary remix attachment points of birds.  This was disputed separately by Naish and myself shortly after the genus was described.  I still don't see how the authors interpret the bumps as posterolateral instead of anterolateral.  I argued the structure was an intermuscular line between the flexor ulnaris and the extensor carpi radialis brevis (sensu Meers, 2003), or flexor digitorum profundus and extensor carpi ulnaris (sensu Gishlick, 2002).  Cuesta et al. state that (besides the triceps brachii which we both agree is back on the olecranon) they reconstructed the anconeus and abductor polices longus and that the bumps are not located between them.  The abductor polices longus (pronator quadratus in Meers) is a more proximodorsally located scar I agree has nothing to do with the bumps.  I think anconeus is another term for the extensor carpi ulnaris, based on Gishlick's figure of Corvus and Hudson and Lanzillotti's (1964) description.  So with the caveats that there seems to be no consensus for muscle names or homology between crocodylians and birds, I don't think Cuesta et al. had the same muscles in mind as I did.

Fortner reports "parts of an associated postcranial skeleton of a small theropod dinosaur recently collected from the uppermost Aguja Formation."  This is another frustrating example of the information-bereft abstract, with the first twelve lines devoted to introduction and background knowledge.  The only other bit of information is- "The specimen exhibits some unique features, but is compatible with identification as either Troodontidae or Dromaeosauridae."  This is very intriguing, as while both eudromaeosaur and troodontine teeth are known from the Aguja, we have Richardoestesia and Paronychodon from there too.  As I think these are microraptorine and basal troodontid respectively, this specimen could fit the bill.  Did anyone get more details?

The only published non-dental remains attributed to Paronychodon- a partial dentary IPFUB GUI D 1 in A. medial, B. dorsal, and C. lateral views (after Zinke and Rauhut, 1994).  It does differ from later Paronychodon in having distal and sometimes mesial serrations.

Harding et al. have the non-dinosaurian abstract I think could be most important to dinosaur studies.  They examined all "published characters for discriminating Sceloporus from the related iguanian lizards Uta and Urosaurus, and for discriminating among species of Sceloporus" for 14 species, "11 of [which] had more than ten individual skeletal specimens, and for four of them sample sizes exceeded 50 specimens."  Perhaps astonishingly "almost all characters published in the literature to identify fossil specimens have no power to discriminate reliably between Uta, Urosaurus, and Sceloporus, nor between species of Sceloporus we examined."  In our field where most species are only known from single specimens, and most known from multiple specimens don't have more than one or two described in detail, what does this mean for our autapomorphy lists?

Holtz et al. report more information on an Anzu specimen (anyone know the collection number?) they announced last year.  Interestingly, only distal tarsal IV is fused to the unfused metatarsus, and "a pair of pronounced cruciate ridges on the plantar surface of metatarsal III" are present as in Elmisaurus but don't extend as far proximally.  This would make it intermediate in pedal morphology between Chirostenotes and Elmisaurus

Maddin et al. present a hypothesis based on the development of skull roof bones in mice and chickens.  In mice (and axolotls) the suture between the frontal and parietal corresponds to the boundary between the neural crest and mesoderm in the embryo.  In chickens, the latter embryonic boundary is within the frontal itself.  Thus the authors suggest the avian 'frontal' is actually a fused frontal and parietal, while the avian 'parietal' is actually a postparietal.  They say that hypothesis "is also supported phylogenetically where data from the fossil record reveal separate frontal, parietal, and postparietal bones are present in all stem lineages of extant taxa, including that of birds (e.g., the stem archosaur Euparkeria)."  The problem I see is that the postparietal in basal archosauriforms is a tiny wedge between the parietals and supraoccipital, while the parietals have the same topological relationships and morphology in these basal archosauriforms that they do in basal dinosaurs.  It seems more likely to me that this is a case like manual homology where the developmental process itself evolves, so that somewhere on the sauropsid line, the neural crest-mesoderm boundary moved into the frontal.  Also interesting would be to know what the state in lepidosaurs and crocodylians is.

Comparison of skull roof in dorsal view of- left, Erythrosuchus africanus (after Gow, 2003); center, Ornithosuchus longidens (after Walker, 1964), and right, Herrerasaurus ischigualastensis (after Sereno and Novas, 1993).  Parietal is blue, postparietal is red.  Maddin et al. suggest the red at left is homologous to the blue at right.

Mannion et al. redescribe the famous 'French Bothriospondylus' (MNHN coll.), presumably based on Moine's (1999) thesis.  It's great that we're getting all of the historical Bothriospondylus material redescribed in the last decade.

McFeeters et al. do the important job of reevaluating Struthiomimus specimens.  Little known to most, the holotype is extremely fragmentary, with most information coming from Osborn's AMNH 5339, Nicholls and Russell's UCMZ 1980.1 and the new RTMP 90.26.1. The authors find "a relatively small partial skeleton from the lower Dinosaur Park Formation" (which based on listed elements must be ROM 1970) to belong to a new taxon of ornithomimid based on several autapomorphies.  This specimen forms the basis of the dorsal snout in Russel's (1972) and Paul's (1988) cranial reconstructions, making those composites.  Another specimen shares some pelvic characters with Qiupalong, perhaps relating to a Dinosaur Park astragalus reported by McFeeters et al. in last year's SVP abstract. 

Nesbitt et al. seem set to provide a detailed description of Asilisaurus, after the original tabloid announcement.  Interestingly, Agnosphitys is said to a basal silesaurid as well, which is the fourth proposed identification for the genus.  Add this to Agnolin's (2015) Jornadas Argentinas abstract proposing Pisanosaurus belongs to the clade, and its membership is expanding markedly.

We also get yet another description of Nothronychus' braincase.  Far be it for me to complain about having too many descriptions of a taxon, but this one specimen of one taxon was described in 2005, 2012 and 2013, and now we'll probably get a fourth portion next year or so.  At least this new abstract is about the previously unrecognized anterior portion, but I'd rather have that time and effort go towards... say "Zunityrannus" or describing the Bayan Shiree therizinosaur postcrania.  Smith et al. report that "there is a supraorbital evagination in this specimen that is currently interpreted as accommodating a well-developed nasal gland in the frontal.  This development has been observed in some other archosaurs, especially marine birds, where it is associated with salt excretion and is consistent with a beach or other evaporitic paleoenvironmental interpretation."  So let's all start our All Yesterdays style marine therizinosaur pics.

Finally for this year, Sullivan et al. report a 'sphenosuchian' specimen sister to Junggarsuchus.  This has the interesting mix of cursorial features with a webbed hand and distal tail sheathed with armor. 

References- Wiman, 1929. Die Kreide-Dinosaurier aus Shantung. Palaeontologia Sinica (series C). 6, 1-67.

Hudson and Lanzillotti, 1964. Muscles of the pectoral limb in galliform birds. The American Midland Naturalist. 71(1), 1-113.

Walker, 1964. Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs. Philosophical Transactions of the Royal Society of London, seies B. 248(744), 53-134.

Russell, 1972. Ostrich dinosaurs from the Late Cretaceous of western Canada. Canadian Journal of Earth Sciences. 9, 375-402.

Paul, 1988. Predatory Dinosaurs of the World. Simon & Schuster: New York. 464 pp. 

Sereno and Novas, 1993. The skull and neck of the basal theropod Herrerasaurus ischigualastensis. Journal of Vertebrate Paleontology. 13, 451-476.

Zinke and Rauhut, 1994. Small theropods (Dinosauria, Saurischia) from the Upper Jurassic and Lower Cretaceous of the Iberian Peninsula. Berliner Geowissenschaftliche Abhandlungen. E 13, 163-177.

Moine, 1999. Datation, condition de depot et position phylogenetique de 'Bothriospondylus madagascariensis' (Damparis,
Jura, France). MS thesis, Memoires de Maıtrise Magistere Sciences de la Terre ENS-Lyon.

Gishlick, 2002. The functional morphology of the forelimb of Deinonychus antirrhopus and its importance for the origin of avian flight. PhD thesis, Yale University. 142 pp.

Gower, 2003. Osteology of the early archosaurian reptile Erythrosuchus africanus Broom. Annals of the South African Museum. 110(1), 1-88.

Meers, 2003. Crocodylian forelimb musculature and its relevance to Archosauria. The Anatomical Record. Part A, 274A, 891-916.

Agnolin, 2015.  Nuevas observaciones sobre Pisanosaurus mertii Casamiquela, 1967 (Dinosauriformes) y sus implicancias taxonomicas. XXIX Jornadas Argentinas de Paleontologia de Vertebrados. Libros de Resumenes. 13-14.

Friday, October 16, 2015

SVP 2015 Day 3

Time for day three.  If I were in Dallas, I'd be waking up early for Technical Session X.

Carrano and Choiniere reexamine Ceratosaurus' forelimb based on the holotype.  The whole thing could use redescription since Gilmore's last one 95 years ago.  While they state "These new data are consistent with the placement of Ceratosaurus as close to (or within) Abelisauroidea", an abelisauroid Ceratosaurus is impossible as Ceratosauroidea predates Abelisauroidea, without even getting into phylogenetic nomenclature. 

Hey, we get more Dromiceiomimus feathers.  van der Reest et al. report on a new specimen preserving feathers on the proximal thigh and dorsal tail, but not ventral tail or distal hindlimb.  The feathers are also branched, moving this trait to the base of Maniraptoriformes.  As the feathers have rachis but lack barbules, it seems Prum's Stage IIIa was correct.

Segnosaurus galbinensis radius and ulna (paratype IGM 100/83), courtesy of Zanno.

Kobayashi et al. describe a new therizinosaur specimen from the Bayan Shiree Formation, where Segnosaurus, Erlikosaurus and Enigmosaurus come from.  While it's notable for having a reduced metacarpal III (and thus perhaps reduced third manual digit), none of the three named genera from that formation preserve enough manual material to evaluate their condition.  The new specimen is potentially comparable to Enigmosaurus and Segnosaurus in that all preserve the radius and ulna.

Funston and Currie report on their fairly complete Horseshoe Canyon caenagnathid.  Supposedly having cervicals "distinct from Epichirostenotes", an "articular ridge is intermediate in size and form between Caenagnathus collinsi" and sternbergi, and autapomorphic manual proportions, it should be useful for resolving caenagnathid taxonomy.  In addition to the expected anatomical details, ulnar "feather scars" are said to be present.

Lu et al. discuss the billionth new oviraptorid from the Nanxiong Formation.  This one's based on at least a skull and is similar to Khaan.  Some of these things have got to be synonymous

Saurornitholestes has been the ubiquitous but rarely described Late Cretaceous American dromaeosaurid.  We've had RTMP 88.121.39 and MOR 660 known since 1988 and 1990 respectively, but both are only mentioned in passing in papers.  Now we have a new almost complete specimen discovered in 2014 (did anyone who saw the talk catch the specimen number?) that includes a skull.  Is the Saurornitholestes osteology finally at hand?

Perhaps the most unusual theropod abstract is from Sorkin, describing a phylogeny for tetanurines.  I'm not sure if it's based on a quantitative analysis or just the noted 'key characters', but it's not similar to the current consensus.  From the abstract, his topology and taxonomy seems to be-


            |--Acrocanthosauridae (incl. Eocarcharia)

Brings you back to the early 90s, doesn't it?  Note the new clade name Euavetheropoda, said to be distinguished by a robust dorsal quadratojugal process.  In any case, the accepted phylogenetic definition for Avetheropoda would put it at the Allosauridae+Coelurosauria node, making Euavetheropoda unintuitively more inclusive. 

Wills describes sixteen teeth from the Bathonian Forest Marble Formation of England.  When analyzed, these plot with dromaeosaurids.  He states "This pushes back the origin of dromaeosaurids from the Kimmeridgian to the Bathonian", but Metcalf and Walker described teeth from the Bathonian Chipping Norton Formation of England as dromaseosaur-like back in 1994.  Maybe these new ones are more securely identified.

Dromaeosaurid-like tooth (GLRCM G.51422) from the Bathonian Chipping Norton Formation in lingual (A), labial (B) and basal (C) views (after Metcalf and Walker, 1994).
Just one more day to go, with quite a few interesting abstracts tomorrow.

Reference- Metcalf and Walker, 1994. A new Bathonian microvertebrate locality in the English Midlands. In Fraser and Sues (eds.). In the Shadow of the Dinosaurs- Mesozoic Small Tetrapods. Cambridge University Press. 322-332.

Thursday, October 15, 2015

SVP 2015 Day 2

And we're on to day two.  Something I noticed about this year's and last year's abstracts is just how many of them are already published in official format by the time the meeting happens (yet another reason the embargo is silly).  I gather one of the big issues facing SVP is how many talks and papers there are, leading to greater expense, more parallel sessions, etc..  If the dinosaur abstracts are any indication, you could cut out a third of them by excluding those that will be published by September.

Pritchard created a new matrix to test the relationships of Sauria, but alas this is one of those abstracts that doesn't actually contain much information.  The most it says is that Protorosauria is para/polyphyletic, which everyone agrees with by now.  I would ask that if your SVP abstract is based on a phylogenetic analysis, please devote at least a couple sentences to describing the topology you found.  Otherwise it's just a tease and I learn nothing.

This was a great SVP for ornithischians.  We've had Arbour revise ankylosaurids, and now Burns is doing the same for Campanian-Maastrichtian North American nodosaurids. He finds Denversaurus is a valid taxon, sister to Panoplosaurus.  So that's another genus from your 1980s dino encyclopedias to dust off.

Denversaurus.  What?  That's not right?...

Continuing the ornithischian train, Barta and Norell report on new specimens of Haya.  The interesting thing here is that they performed two analyses- one with each specimen coded as a separate OTU, and the other with one Haya OTU that was coded as polymorphic when specimens differed.  In the first, Haya emerged as a basal thescelosaurid, but in the second it was a basal neornithischian.  This is presumably because PAUP/TNT finds it most parsimonious to choose a mix of states for the polymorphic characters that isn't found in any actual specimen.  It's concerning because being a lumper myself, I code e.g. Microraptor and Archaeopteryx as single OTUs.  Is that affecting their relationships in my analyses? 

Shelley et al.'s abstract is an example of two things I like.  First, figuring out where all of those extinct mammal groups go using a molecular scaffold for the topology.  Second, actually describing the results of the study- "Our phylogenetic analysis places "triisodontids" as a basal member of Euungulata within Laurasiatheria. "Triisodontidae" forms a paraphyletic stem of Mesonychia with Oxyclaenus most closely related to a monophyletic Mesonychia.  "Triisodontids" plus Mesonychia are closely related to a clade comprised of the arctocyonids Mimotricentes, Deuterogonodon and Chriacus."  Ahhh, actual information...

Besides the usual morass of Yixian and Jiufotang birds (including Parapengornis, which I think is just Pengornis), we get another specimen from the lower member of the Huajiying Formation.  This earlier horizon has otherwise only yielded Confuciusornis zhengi, Protopteryx, Eopengornis and Archaeornithura.  Hu et al.'s new enantiornithine is said to have a Liaoningornis-like sternum, which could cement the affinities of that genus. 

The Norman-Barrett team's on the basal ornithischian case again, this time with Baron et al.'s redescription of Lesothosaurus postcrania.  This is needed, as Sereno (1991) mostly described the skull and thus we've had to depend on Thulborn's work from 43 years ago.  They find Stormbergia to be based on older individuals of Lesothosaurus, which as a lumper, does not surprise me.  The genus emerges as a basal neornithischian.  This should be a good paper once it's published.

Holotype of "Morosaurus" agilis (USNM 5384) posterior skull and anterior cervicals in left lateral view (after Gilmore, 1907).

Finally, Whitlock and Wilson redescribe the hitherto enigmatic "Morosaurus" agilis.  Based on a braincase and anterior cervicals, it turns out to be a diplodocid.  While apparently not Apatosaurus (in which the abstract seems to include Brontosaurus) or Galeamopus, the newly exploded Morrison Diplodocidae leaves open numerous possible identifications- Supersaurus, Amphicoelias, Kaatedocus, Barosaurus, Diplodocus...  I'm not sure I believe its affinities can't be narrowed down further.  For instance, Lovelace et al. (2007) stated small cervical pleurocoels were diagnostic for Supersaurus, and agilis has large pleurocoels.  Tschopp and Mateus (2013) proposed numerous characters to distinguish Kaatedocus from other diplodocids, including a postorbitally restricted squamosal that agilis seems to have, and a postparietal foramen agilis seems to lack.  Maybe published characters have issues that I'm not aware of as a theropod worker, or maybe Gilmore's description is misleading, but I find hard to believe that something as complex as a braincase and posterior skull can't be distinguished between Kaatedocus and Diplodocus (even if Amphicoelias and Barosaurus can't be compared).

Join me again tomorrow, when we open with those sweet, sweet theropod abstracts...

References- Gilmore, 1907. The type of the Jurassic reptile Morosaurus agilis redescribed, with a note on Camptosaurus. Proceedings of the United States National Museum. 32(1519), 151-165.

Sereno, 1991. Lesothosaurus, "fabrosaurids," and the early evolution of Ornithischia. Journal of Vertebrate Paleontology. 11(2), 168-197.

Lovelace, Hartman and Wahl, 2007. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional Rio de Janeiro. 65, 527-544.

Tschopp and Mateus, 2013. The skull and neck of a new flagellicaudatan sauropod from the Morrison Formation and its implication for the evolution and ontogeny of diplodocid dinosaurs. Journal of Systematic Palaeontology. 11, 853-888.

Wednesday, October 14, 2015

SVP 2015 Day 1

While again too poor to attend SVP, I thought I would provide my thoughts on the abstracts that interest me like I did last year.  The abstracts book can be download free at this link.  When adding abstracts to the Database, I noticed an issue that's been constant throughout the years- the titles are in UPPERCASE.  This makes copying them useless, which means everyone citing abstracts has to rewrite them.  This can only lead to more typos and serves no obvious purpose since the titles are already bolded to distinguish them from the rest of the text.  Does anyone else agree they should have normal capitalization?

This year there are no less than three abstracts marked as WITHDRAWN.  One is by Egberts and concerns wearing gloves when handling specimens to prevent skin oils damaging the fossils.  Another is by Spindler, about a supposed Carboniferous therapsid specimen.  The third by Parsons and Parsons involves aerial forelimb motion in Bambiraptor and Deinonychus.  I wonder why these three abstracts didn't make it.

Wilson reports that of three histologically sampled Pteranodon specimens, the largest and smallest are rather mature, while the medium-sized one is immature.  While she interprets this to mean "there may be a large amount of adult body size variation in Pteranodon" or possibly that "the smallest specimen sampled is from a large Nyctosaurus specimen", Peters' idea of taxonomic instead of ontogenetic variation in Pteranodon seems viable too.  Is this a case of Peters being right?

Andres (and posthumously Langston) signal the beginning to the end of the deplorable situation pterosaur workers have been in where Quetzalcoatlus' holotype has been inaccessible due to the TMM embargoing it for decades.  All it took was the eventual death of the person monographing it.  :|  Now if we can just get Pelecanimimus out of the same rut, so that those who have the thesis describing it will distribute it and allow others to photograph the material described over two decades ago...

Frontals of Bellusaurus sui referred specimen IVPP V17768.7 (left; after Mo, 2013), Europasaurus holgeri referred specimen DFMMh/FV 162 (center; after Marpmann et al., 2015), and Camarasaurus lentus referred specimen CM 11338 (right; after Gilmore, 1925) showing two characters reported by Moore et al. as shared between the former two genera- elongate frontal and deep orbital concavity in frontal. 

Moore et al. report on new Bellusaurus cranial elements, juvenile like the previously known material.  Interestingly, these support a macronarian position, and close relationship with Europasaurus.  No update on the oft-hypothesized synonymy with Klamelisaurus, as that genus only preserves teeth and postcrania.

Finally, we have the abstract supposedly authored by Chinzorig, Kobayashi, Tsogtbaatar, Mahito, Rinchen and Shigeru...?  Someone messed up somewhere, because of course the actual authorship using surnames should be Tsogtbaatar, Kobayashi, Tsogtbaatar, Watabe, Barsbold and Suzuki.  This one's going to be tedious to find/cite in the future.  The find itself is a diagnostic ornithomimid tarsus and pes from the Djadokhta Formation of Mongolia, unfortunately not comparable to the previously described cranial and vertebral material (IGM 100/987 and 100/1245) from that formation.

Join me tomorrow for Day 2 talks and posters...

References- Gilmore, 1925. A nearly complete articulated skeleton of Camarasaurus, a saurischian dinosaur from the Dinosaur National Monument. Memoirs of the Carnegie Museum. 10, 347-384.

Mo, 2013. Bellusaurus sui. Topics in Chinese Dinosaur Paleontology. Henan Science and Technology Press. 155 pp.

Marpmann, Carballido, Sander and Knötschke, 2015. Cranial anatomy of the Late Jurassic dwarf sauropod Europasaurus holgeri (Dinosauria, Camarasauromorpha): Ontogenetic changes and size dimorphism. Journal of Systematic Palaeontology. 13(3), 221-263.