II CLPV talk summaries: Day 3

[dinoboygraphics@aol.com]

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

www.skeletaldrawing.com