[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
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
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.
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443