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II CLPV talk summaries: Day 3

And here I am for the last installment. This one will be shorter than the others; I missed the morning talks to help polish Dave Lovelace?s talk (I was a coauthor), and to sleep in a little? Also, like the first day, most of the talks were not in English. Enough preamble, on to the summaries:

Day 3: Friday the 12th

Claudia Ribeiro gave a talk in Spanish on dinosaur eggs (end eggshell pieces) that are being collected in Late Cretaceous deposits in Argentina. They are striving to increase stratigraphic resolution on the eggshell bearing units there. They identified three morphs of presumed sauropod eggs, and one ootaxa of egg that was interpreted as oviraptorid. Most of the talk consisted of defining the ootaxa based on eggshell texture, thickness, and of course microstructure. See Dinosaurs, Eggs, and Babies if you are interested in an overview of this taxonomic system.

Nicholas Geist gave a talk the evolution of the archosaurian hard-shelled egg, and the requisite changes in the uterus, using crocs and birds as examples. Unlike the abstract, the talk did not cover temperature-dependent vs. chromosomal sex determination, and he did not posit any link between archosaur egg production and dinosaur extinction at the K/T boundary (good call!). The talk did not really present anything new, but it was a good overview of croc and bird reproduction. He pointed out that the differentiated areas of the reproductive tract in archosaurs (e.g. adding albumen as opposed to shelling, which happens further down the tract) probably precludes uterine retention of eggs, making it unlikely for archosaurs to evolve ovoviviparity. I think that is likely correct, although they are not the first to make the suggestion.

Unfortunately I got little from many of the other talks, most of which were in Portuguese. At 5:30 fellow WDCer Takehito Ikejiri (he goes by ?Ike?) gave a talk on sexual dimorphism in Camarasaurus. I had not seen his data before, and I was impressed. Ike analyzed most of the fairly complete specimens of Camarasaurus, and discovered two persistent ?morphs?. Camarasaurs with more robust limbs had differences in the axial column and their ischial morphology. These differences were always consistent, even across the different species of Camarasaurus. Also, juvenile specimens of Camarasaurus do not evince any dimorphism. So he concluded that these are truly secondary sexual characteristics, and they do not show up until sexual maturity. He concluded by hypothesizing that the robust individuals were male, and by cautioning against assuming that these features will apply to other sauropods (without additional investigation).

Last up for the conference was Dave Lovelace. He was presenting our data on the new specimen of Supersaurus that has been worked on for several years at both the Tate and now the WDC. Unlike the mess of bones associated with the BYU quarry (Dry Mesa), the WDC Supersaurus quarry contains a single sauropod individual. This showed that a number of bones that have been referred to Supersaurus in the past were in serious error. For example, referred BYU caudal bones have often been cited as evidence that Supersaurus was closely allied with Barosaurus, but in fact the caudals from Dry Mesa probably ARE Barosaurus. The caudals from the new Supersaurus are very apatosaur-like. Also the pelvic elements found at the WDC quarry show that the attribution of the apatosaur-like pelvis from BYU is correct. You can maybe see where this is going, but the phylogenetic assessment finds that Supersaurus is a long-necked apatosaurine diplodocid, along with Apatosaurus and Suuwassea. Seismosaurus is the sister taxa to Diplodocus (more coming in that vein in the future?), with Barosaurus as the most primitive diplodocine. So apatosaurines are more diverse than previously thought, and we speculated they may be an exclusively North American clade. Let me add a shout-out to co-author Bill Wahl, who has toiled tirelessly on this project since the specimen was found in 1996. Congrats to him and Dave for seeing this project through!

That?s a wrap. The meeting was a lot of fun, and I got to meet a lot of South American colleagues I may not have otherwise had the pleasure of meeting. The dinner had the best beef Wellington I have had in my life and a host of other good food (and desserts!). In SVP-like form, there was music and dancing after the meal (and a brief series of congratulatory-sounding talks in Portuguese). I hope some of you found these summaries interesting. Over and out...

Scott Hartman Science Director Wyoming Dinosaur Center 110 Carter Ranch Rd. Thermopolis, WY 82443 (408) 483-9284