After registering this morning, we attended a couple of talks on Pleistocene fossils, including Blaine Schubert from East Tennessee State University on the giant short-faced bear, Arctodus simus (the example above is from the Sam Noble Oklahoma Museum of Natural History.) Schubert showed photos of several new Arctodus specimens, including the first known examples from Florida and from Saltville, Virginia (VMNH has a permanent exhibit on fossils from Saltville). He suggested that extreme sexual dimorphism accounts for the variation in body size in Arctodus fossils, and his Carbon-14 data indicate that humans and short-faced bears overlapped in North America around 10,000 years ago.
Darryl de Ruiter of Texas A&M presented on Australopithecus (a member of our on family Hominidae). A standard idea in human evolution is that ancestral hominids such as Australopithecus preferred open, arid grassland habitats (savannahs). de Ruiter’s data indicate that australopithecines didn’t prefer savannahs, but that instead they were simply capable of surviving there where other primates couldn’t.
Australopithecus robustus (cast from the Cleveland Museum of Natural History).
Eleanor Weston and Adrian Lister (both from the Natural History Museum, London) presented on dwarf hippopotomus species from Madagascar. Their central observation is that dwarf hippos have brains that are unusually small, even when the size of their bodies is taken into account (in other words, dwarfism results in abnormally small brains.) As Weston pointed out, this has implications for Homo floresiensis, the so-called hobbits from Indonesia (see Joel Achenbach’s comments and my earlier post.) Weston and Lister’s study indicates that the small brain size in H. floresiensis can be explained by dwarfism, without resorting to pathologies such as microcephaly.
I skipped lunch to attend a symposium on teaching evolution (VMNH Executive Director Tim Gette was also there.) Later I discovered that I couldn’t pull off “floating head doctor” (“Scrubs” fans will understand the reference), so I went to a session on taphonomy (how fossils are preserved) while my wife Brett attended a different session on marine reptiles.
The taphonomy talk was by Randall Irmis, Nick Pyenson, and Jere Lipps (all from US-Berkeley) on the Sharktooth Hill marine bonebed from California. This bonebed extends over a huge area, and has certain similarities to the Carmel Church bonebed that VMNH has been excavating in Virginia. These similarities include a thin (< 1 meter thick) bonebed, deposited on an erosional surface, dominated by sharks and whales, with no invertebrates and extensive bioturbation. Sharktooth Hill is at least a million years older than Carmel Church (15-16 million years old.
Irmis and his coauthors interpret Sharktooth Hill as a “time-averaged death assemblage”, meaning that the bones come from animals that lived somewhere else and were carried to the site after death (by currents), and that this took place over a fairly long period of time. Carmel Church has some differences (for example, the presence of skeletons instead of individual bones, and lots of bite marks from sharks on the whale bones) that indicates a different origin for Carmel Church, although we don’t yet know what that might be.
Meanwhile, Brett was listening to F. R. O’Keefe’s (Marshall University) talk on a partial plesiosaur skeleton from near Shell, WY, not too far from VMNH’s dinosaur excavation (in fact, I think I remember him mentioning this specimen when we were staying at the same campground in Shell a few years ago). The plesiosaur had a strange mass in its abdomen, which included several bones from a baby ichthyosaur. O’Keefe believes it may have been an aborted embryo (ichthyosaurs gave live birth) that was scavenged by the plesiosaur.
Finally, Brett and I joined up again to listen to a talk on Pleistocene cave fossils from the Andes Mountains in Peru by Bruce Shockey (American Museum of Natural History), with co-authors Rodolfo Salas Museo de Historia Natural), Francois Pujos, and Jean-Loup Guyot, and Patrice Baby (Institut de Recherche pour Développement). They reported on a number of new specimens, including sloths, puma, sabre-toothed cats, vicuñas, horses, and others, from caves up to 14,000 feet above sea level. Rodolfo showed some of these specimens during my last visit to Lima, and they’re very diverse and amazingly well-preserved. Some of the sloth remains reported today are remarkable in that they include preserved keratin (a protein found in claws), even though the remains are 30,000 years old.
Late afternoon today was the first of four poster sessions. Among the things I saw: bone-bearing coprolite (fossil dung) preservation, Jefferson’s ground sloths in Iowa, turtle tracks in the Triassic of Wyoming, low-cost 3-D laser imaging, Paleocene snakes from Bolivia, and ichthyosaurs from Alaska.