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SICB Report, part 2 (not quite as long)



Okay, part 2.

First, some brief comments:
SICB is a conference that more paleontologists (vert & invert) should be
going to.  Not to say that there weren't some there: in addition to those
listed in the part 1 report, paleomammalogists Blaire Van Valkenburgh &
Audrone Biknevicius were there, Rick Blob was presenting the neontological
side of his work on limb mechanics (his dissertation work also included a
lot on synapsid limb evolution), there were posters on scaphopod ("tusk
shell") paleontology and on cervid (deer) evolution with regards to breeding
behavior and Greg Erickson's (of _T. rex_ tooth and turd fame) poster on
mudskippers and so on.  In fact, there was a whole session on starfish
evolution, which obviously featured some paleontologists.  Nevertheless,
there were very few of us bone jockeys (and even fewer shell jockeys).

Which is a shame, because a LOT of interesting work is being presented on
modern animals which has a direct bearing on paleontology.  I often see
comments on this list along the lines of "well, surely someone has examined
[fill in the blank with your favorite modern animal adaptation]."  It turns
out that in a lot of cases that just isn't so.  Some really interesting
aspects of modern animals are still under investigation, as the
presentations at SICB attest.

One drawback with SICB is the price: $220 for members early, $320 for
non-members early, $205 for non-member postdocs early.  Ugh.  On the other
hand, the price for non-member students is $130, for student/high school and
community college teachers is only $70.  There are four full days of talks,
with eight to eleven different sessions going simultaneously (so a lot more
like the American Geophysical Union or Geological Society of America than
like SVP in terms of scale).

In any case, if you are at all interested in functional morphology (and
particularly if you are a student) I would encourage you to attend.

So, on to the non-feathers talks.
Obviously, there was too much going on for me to have seen more than a
fraction of it, and I can't be expected to report on all of it, but here are
some highlights that dinosaur fans might find interesting.:

D.J. Irschick & B.C. Jayne presented a paper on the 3-D kinematics of
lizards running at high speeds.  Most previous work on limb kinematics has
been on slow moving individuals, but (as the presenters pointed out) many
lizard species are adapted to high speed locomotion.  They presented some
great stills and video of lizard species in fast runs.  They were looking at
smaller lizards, and found that they run bipedally in different ways than
(say) frilled lizards.  In fact, some of the faster small species they
examined ran with their hips very high (for the body size), the body held
almost horizontally, the feet entirely digitigrade throughout the step
cycle, so that none of the metatarsus contacted the ground ("Sound
familiar?" commented Jim Farlow...).  In the case of _Callisaurus_ (sorry,
can't remember the common name) the tail was curled up at the base, and the
stiff distal portion held vertically!  (The tail reminds me a LOT of
dromaeosaurs, so it's got me wondering...).  In any case, a fast running
lizard is not a sprawller at all.

I missed a series of talks on vertebrate locomotion I wanted to see because
of the Feathers talks: K. Earls latest on take off of starlings (saw some of
her preliminary work at Bristol in 1997), Gleeson et al.'s talk on why the
cost of locomotion often does not reflect cost of activity (of obvious
importance for those concerned with dinosaur energetics), and S.M. Reilly's
talk on the kinematics of the sprawling-to-erect transition.  I did get to
see Stuart Sumida & Elizabeth Rega's back-to-back talks about skeletal
biology, mechanics, anatomy, sexual dimporphism, and animation: cool things
for teaching purposes (must get "Chuck Amock"!), learned some stuff about
the new Disney Tarzan and previous Disney and other animated movies, and had
a good time.  (Sumida & Rega's party was great, especially as I missed the
one at SVP.  Unfortunately hotel security only told us to quiet down once,
not twice: I figured it was because we didn't have enough rowdy
paleontologists...).

Rick Essner presented a paper on the biomechanics of gliding in the flying
squirrel (_Glaucomys volans_), which showed first off that there is a major
leaping component to their "flight" (i.e., they aren't just dropping from
the trees and gliding, as some have argued).  Furthermore, the ballistic
portion of their jump isn't at 45 degrees (as some have thought, because
this would maximize total distance travelled).  Instead, it is closer to 23
degrees or so: this way they travel a lot further faster.  Other good stuff
in there, too.  It goes to show that less is known about gliding in living
animals than a lot of people assume (or model in their origin of flight
studies...).

Similarly,  J.J. Socha presented a paper (which I missed, but was updated
on) on the "flight" kinematics of the flying snake _Chrysopelea paradisi_.
Although they sometimes start the glide from a controlled fall, they too can
use a propulsive phase (either horizontally, or occasionally at a more
vertical angle).  I wish I could have seen the video, though: as I entered
the room just as people were leaving, I heard a lot of "That was so
*cool*..." comments.

There were a fair number of interesting talks at the Symposium on the
Function and Evolution of the Vertebrate Axis.  I finally got to see
(legendary morphologist) S.A. Wainwright give a talk: I will steal a few of
his bits for my teaching...  D.A. Pabst presented work showing convergence
in soft tissue features (peripheral cross-helically wound connective tissue,
etc.) between tunas and cetaceans, which function as springs against the
axial skeletomuscular system.  Blubber ain't just for fat storage!!  It has
me wondering about ichthyosaurs...

Steve Gatsey presented a review of the structural and functional evolution
of the theropod tail.  I was familiar with a lot of this (although the
electromyographs of different muscles during slow walk, fast walk, and
flight of a pigeon was still very cool).  I was very happy to see it at the
meeting, especially after so many people at the Feathers conference were
making it seem as if there was this huge morphological gap between "The
Theropod Condition" and "The Avian Condition" (as if either non-avian
theropods or birds were all identical...).  Some really cool aspects of the
soft tissue of bird tails were explored.

As I said, Gatsey's talk was mostly stuff I was familiar with: if it had
been new to me, I would have pegged it as the best dino-related talk at the
meeting.  Instead, that honor (for me) goes to Carrier & Farmer's (I think)
talk on archosaurian respiration and locomotion.  It was a damned shame that
most of the people at the Feathers symposium had left by the time it was
presented, because it directly applied to the work of some of them (Ruben,
Geist, etc.), and would certainly have interested others (Farlow, Currie,
Dodson).  Doubly unfortunate was the fact that the title, authorship, and
abstract had changed from that listed in the abstract volume: if the others
had known about it, perhaps they would have stayed.

What Carrier and (I think) Farmer did was examine respiration and lomotion
(and their interrelationship) in modern archosaurs, and speculated on the
same in various extinct groups.  They looked at the hepatic piston/diaphragm
breathing in living crocodilians.  Not just "modern crocodilians", as most
previous workers (through dissections, etc.), but in living *breathing*
crocs.  With electromyographic studies and such.  It turns out that the
hepatic pistion as found in modern crocs seems to require a mobile pubis,
something crocs have (the pubis does not meet the acetabulum as in most
amniotes, and in fact is on a joint with the ischium & ilium) but which
dinosaurs did not.  In fact, there are muscles running from the ischium to
the pubis which are involved in breath and recovery.  Like many active
animals, crocs breath in synch with the step cycle while moving fast.  Birds
breath with a combination of the movement of their huge sterna and rocking
of the pelvic & tail region.

So, what about extinct forms?  If theropods were diaphragm breathers, they
were not doing it the same way crocs do: their pubes were immobile and fully
incorporated into the acetabulum.  Carrier & Farmer, based on some earlier
work by Leon Claessens, hypothesized a gastralia-based breath pump for
theropods.  Although having gastralia is primitive for amniotes, theropod
gastralia have some very interesting adapations.  In the system they
suggested, theropod breath would be in synch with the step cycle (and,
curiously, 180 degrees phase shifted from the breath cycle of neornithine
birds!).  As with many things, the shift from a primitive theropod breath
system to the modern bird breath system would involve a series of
transitions rather than one big jump, so that advanced non-avian
maniraptorans (like dromaeosaurids) and basal birds (like Archie) would
presumably be more similar to each other than to breathing in _Eoraptor_ or
neornithines, respectively.  There is some question about the myology of
this system (and I wonder about the change from the more basal theropod
ischial condition to the more derived, slender and/or reduced condition in
coelurosaurs), but it should prove interesting working it all out.

Ornithischians and sauropodomorphs weren't dealt with to any great detail.
It was suggested that pterosaurs were (curiously) a combination of croc AND
neornithine type breathers: their pelvis morphology suggested the
rocking-breaths of birds, and their prepubis bone as the functional analog
to the pubis of crocs in a hepatic pistion.  Carrier alluded to some study
on breathing in modern marsupials suggesting that the epipubic bone
("marsupial bone") was also a functional analog to croc-pubes in the
diaphragm breathing of marsupials: sounds intriguing, and must look into it.

I don't know when they plan on publishing this study, but I look forward to
it.  It was a great intergration of skeleton, soft tissues, dissections,
studies of living animals, and speculations.

All-in-all, a busy time.  Now to get ready for the Ostrom Symposium... :-)

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661