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.

4 comments:

  1. I've actually been aware of the diplodocid nature of Morosaurus agilis for a long time --- in their SVP abstract, Tidwell et al. (2005) noted that USNM 5384 is not only diplodocid, but features cranial characters consistent with diplodocines rather than apatosaurines. They simply considered it synonymous with Diplodocus longus because USNM 5384 was found a meter away from YPM 1920 (holotype of Diplodocus longus), potentially implying that USNM 5384 is the same individual as YPM 1920 (not to mention the fact that Tschopp et al. 2015 re-identified USNM 2673 as Galeamopus sp.).

    Tidwell, V., K. Carpenter, and C. Miles. 2005. A reexamination of Morosaurus agilis (Sauropoda) from Garden Park, Colorado: Journal of Vertebrate Paleontology 25(supplement to 3):122A.

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  2. Yeah, Tidwell et al. (2005) is why "Morosaurus" agilis is where it is on the Database's cladogram. What's USNM 2673 have to do with it though?

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  3. If the dinosaur abstracts are any indication, you could cut out a third of them by excluding those that will be published by September.

    On the one hand, yes. But a presentation on a recently published paper isn't automatically useless. It makes more people aware of the paper, gives them an opportunity to discuss it with the authors, gives the authors an opportunity to respond to recent criticism... and last but not least, many institutions only fund travels to conferences for people who are going to present something there. Big names could find themselves unable to attend if the publication process is a bit faster than they expected back in April or May when the deadline for submission was.

    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.

    Adam Pritchard got different results in different analyses. The diapsid mess is a step closer to resolution, but there's still a long, long way to go! And the Mess of Enaliosaurs wasn't even included (yet).

    Shelley et al.'s abstract is an example of two things I like.

    Soon, we'll go from having zero serious morphological analyses of placental phylogeny to two (Shelley et al., and Halliday)!

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    1. The funding point is a good one. The online dinosaur community seems well structured enough that we're aware of every paper the month it comes out if not the day. Maybe other areas of vert paleo are different though.

      Also Zack's (2009) thesis analysis of placentals.

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