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II CLPV talk summaries: Day 1

Hello fellow DMLers,

Greetings from beautiful Rio de Janeiro! I thought I?d post some summaries of the talks for those of you who are interested.

First, a few general observations: The coffee here is fantastic! It can best be described as a really strong cup of espresso. The food at the conference is far, far better than what is normally served at SVP. I understand that SVP has a different set of funding issues for their annual meeting, so no offense intended to the organizers, but compliments really must be paid to our Brazilian hosts for both the quality and the sheer quantity of the food they provide. While everyone here is very friendly, and most speak at least some English, on the first day a large number of talks were given in Portuguese. Since I am only semi-competent at Spanish, and Portuguese pronunciation baffles me, I cannot provide many details from those talks. With that caveat, on to the talks from Day 1:

Day 1: Wed. the 10th.

I missed the talks until 11:00, as I was putting the finishing touches on my own presentation. My apologies to lepidosaur phylogeny fans, as I understand there was some cool stuff.

Bruce MacFadden gave a very convincing talk using tooth isotope ratios to throw doubt on the traditional dichotomy between inferred eating habits of high-crown toothed mammals (usually interpreted as open grassland grazers) and low-crown toothed mammals (forest browsing). He showed a Florida paleocommunity with six genera of horses, and despite all of them being hypsodont (high crowned), only two genera showed tooth isotope ratios consistent with exclusive grassland grazing. Two of them were consistent with exclusive forest browsers, and the other two showed intermediate isotope ratios. He speculated that the same thing may be happening in South American faunas that are overly abundant in toxodont taxa.

After lunch Michael Benton gave an hour long overview of his work in Russia, which has the goal of delineating a good terrestrial P/T sequence there. It was filled with a number of humorous anecdotes, including a photo of an enterprising individual who was selling fermented mare?s milk in the countryside of western Russia. The scientific progress report from the project is that they have a good enough isotope series to corroborate the classical Russian location of the P/T boundary. They hope to get some radiometric dates, and between those and sedimentological sampling establish whether they have a continuous terrestrial series or if there is an erosive contact present. A continuous section will let them evaluate hypotheses about tetrapod faunal turnover at the P/T boundary.

Ralph Molnar gave an amusing talk about an incomplete pterosaur skull he is describing with Richard Thulborn. Apparently they sent the manuscript to a journal (which he did not name), who then lost it for almost two years. After it was found and sent back, the authors (who apparently didn?t want to be outdone by ?mere? editors) lost it themselves for another 18 months, at which time they had both retired from their positions. So a few more years pass, and they decided to go ahead and publish the specimen here at II CLPV, since they ?didn?t have anything better to do?. It is apparently an Early Cretaceous pterodactyloid from Queensland, but there aren?t enough diagnostic characters to say much more about it.

There were some interesting looking talks in Portuguese about South American avian faunas, and (yay!) one in Spanish about using comparative morphometrics to estimate the feeding preferences of extinct penguins. The punch line was that there was at least as large a diversity of feeding habits amongst the extinct penguins she examined as there is today.

One of Alexander Vargas? students (sorry, the abstract volume only named Vargas, and my notes appear to be inadequate in this regard) gave a talk in Portuguese about the developmental identity of the manual digits in extant birds. Drawing upon the abstract, and supplemented by the slides (both of which were in English), I am happy to relay that genetically speaking bird fingers are indeed 1,2,3, not 2,3,4. In tetrapods Hoxd12 is not expressed in digit 1, and digit 1 is the last to express Hoxd13. Well, the condensate that becomes the equivalent of digit one (by dinosaur morph standards) follows this gene patter. There may well have been a homeotic shift in condensates such that the genes from digit 1 are expressed in condensate 2, but that of course is completely consistent with the theropod origin of birds. Not much of a surprise, but still nice to see established empirically!

Terry Jones delivered a paper by him and the Rubenite clan. The gist of it was that feathers usually fossilize when the bacteria attempting to break down the cartilage autolithify, creating a microscopic cast around the feather. They SEMed a few specimens from China of different birds and non-avian theropods, and concluded that while Sinornithosaurus does indeed have feathers, that Sinosauropteryx and Beipiaosaurus do not. I got the impression that very few people in the audience were convinced by the data. For starters, they did not have good enough sampling of Yixian theropods. For example, they did not test the fur-like feathers of Sinosauropteryx, Microraptor, or Caudipteryx; even though they accepted that the contour feathers were actual feathers (duh!). Nor did they test scales from, say psittacosaur specimens to see how keratinous structures that were histo-chemically different from feathers would preserve. In their defense, Terry said they did not get much choice in their samples, as that call was made by Chinese authorities. I sympathize with the difficulty that arise from working with foreign specimens, but they should never have made the conclusions they did with the samples they were afforded. For example, they claimed without the slightest bit of supporting evidence that not only is ?dino-fuzz? not feathers (which itself is defensible), but that they aren?t even keratinous (and, they conclude, most likely collagen). In the absence of comparative taphonomic data to show how other keratinous structures preserve (e.g. scales or the dino-fuzz of theropods with morphologically modern feathers) this is an utterly baseless claim. At best this is evidence that the insulatory structures that comprise ?dino-fuzz? had a different molecular make-up than fully modern feathers, which would not be a huge surprise (evolution often proceeds on both histological and morphological levels simultaneously). At worst it was a waste of time. Terry, however, is a great guy, and I don?t mean this as a personal attack on him in any way.

I gave the next talk, which some of you already know was on the origin of avian flight. I made a number of methodological critiques on previous attempts to understand the origin of flight, which I won?t bore you with here unless someone is interested enough to really warrant that much space (it?ll be in the paper though!). I did make a rigorous comparison between extant ?analogs? for arboreal gliding organisms and theropods, including a reconstruction of the pelvis and femora of Microraptor (based on specimens described by Hwang et al.) that show Microraptor could not laterally spread its hind limbs. I also mapped characters against recent cladograms to show that the characters associated with arboreality in birds show up very late, much later than the avian flight stroke and aerodynamic feathers. Hence, I concluded that feathers and the aerodynamic surfaces they create (though not necessarily powered flight) are more likely to have evolved in terrestrial cursors. I also discussed WAIR. I pointed out that successfully engaging in wing assisted incline running requires a derived form of the avian flight stoke (i.e. laterally facing glenoid, morphologically modern feathers, and the musculature to flap them with sufficient force) to pull off, so WAIR is unlikely to have provided selective pressure leading to the origin of those structures. It may, however, have played a role in the later transition to powered flight, the transition from terrestrial to arboreal habitats, or both.

I know many on the list would disagree offhand, but I hope when the paper comes out you will be convinced that there is only the weakest of support from comparative functional morph and from phylogeny for the classical trees-down view of avian evolution. Despite the intuitive appeal, wings themselves and the avian flight stroke appear to have shown up without an arboreal gliding phase. Whether the actual transition to powered flight occurred in the trees may be a different story.

Willem Hillenius gave the last talk of the day (once again coauthored by the whole slew of Rubenites). Ironically, I don?t disagree with the conclusions in his talk, although I greatly disagree with some implications in his abstract and throughout much of the presentation. His conclusion was that based on characters of the sternum and pelvis, pre-ornithurine birds (and non-avian theropods) did not achieve the same level of respiratory capability that ornithurine birds have, and he said explicitly that ?he couldn?t say for sure whether they had ectotherm oxygen consumption rates, sub-avian rates, or something in between?. That is perfectly acceptable, and totally out of line with the abstract?s indefensible false dichotomy between ?avian endothermy? and ectothermy. Extant ornithurine birds have by far the highest oxygen consumption rates of all tetrapods, and I don?t doubt for a moment that more primitive birds (and all non-avian theropods) had lower oxygen consumption rates. That in no way is positive evidence for ectothermy amongst those groups, and as I said, Willem did not in fact conclude it was. The abstract title and much of the talk, however, gave the strong impression (and I talked to a number of people to get the opinions of others) that pre-ornithurines were ectothermic.

After the talks we enjoyed a lovely reception at the Museu Nacional, in which servers appeared to compete to see who could stuff the most appetizers and/or alcohol into paleontological stomachs in an evening. A great time was had by all.

There were some fantastic talks on early dinosaur evolution today; I will post those as soon as I have time to get them typed up.

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