After lunch, Timothy Gaudin, Greg McDonald, and Ascanio Rincón kicked off the afternoon session by looking at the relationships within the sloth family Megalonychidae, which includes such diverse forms as the extinct giant ground sloth Megalonyx and the extant two-toed sloth Choloepus (above example from the Henry Doorly Zoo). Somewhat surprisingly, the living Choloepus seems to be most closely related to megalonychids that lived on Caribbean islands as recently as a few thousand years ago.
Steve Wallace continued his ongoing studies of red pandas, looking at relationships within the family (Ailurus fulgens below from the Mill Mountain Zoo). Red panda studies have taken off in the last few years, and it’s interesting to see a talk in which nearly all the cited papers were published after 2000. Even with the limited material from this group, progress is starting to be made on working out how they evolved and dispersed.
The half-life of uranium-to-lead decay is generally too long to be useful in dating young sediments. However, as Curtis McKinney pointed out, uranium decays in steps and the individual steps have much shorter half lives. Uranium 234 to Thorium 230 has a half-life of just 75,200 years, making it useful for dating Pleistocene tooth enamel.
Girish Tembe attempted to use CT scans to study the enamel ridge patterns in horses from the Blanco Formation in Texas (including Equus simplicidens, like the example below from the Texas Memorial Museum); traditional methods for these studies require cutting the tooth in half. It looks like the may be some promise to the technique, but it requires high-resolution (and expensive) scans to work on something as small as a horse tooth.
Amanda Giesler described her upcoming work on Pleistocene microvertebrates from cave deposits in southern China. She’s already discovered some of the challenges that can face a new graduate student, particularly one working overseas: language barriers, different collecting standards, and a poor understanding of the modern fauna.
Dana Ehret and Benjamin Atkinson discussed the fossil record of diamondback terrapins from the genus Malaclemys (such as M. terrapin pileata, below, from the Dauphin Island Estuarium). While they live up and down the east coast today (as far north as Massachusetts), their fossils are only known from the southeastern US, and only from the Pleistocene. Ehert and Atkinson suggest that their limited fossil record may be due in part to the habits of Malaclemys, which is only found in coastal salt marshes.
Sharon Holte took us back to sloths, specifically Megalonyx jeffersonii (example below from the Joseph Moore Museum). The ACb-3 Cave in Alabama has produced at least 7 individuals of M. jeffersonii, including several different growth stages, which will provide an excellent opportunity to study Megalonyx ontogeny.
Richard Hulbert, Jason Bourque, Peter Meylan, and Art Poyer reported on the Millennium Park, a Pleistocene fossil site near St. Petersburg, Florida. There are surviving remnants in central Florida of prairie ecosystems, but essentially no vertebrate fossil deposits that can be attributed to prairie environments have been found. Millennium Park, which is dominated by prairie taxa such as Bison (below), may be the first.
Leigha King and Steven Wallace discussed the problem of the relationships of the American lion, Panthera atrox. P. atrox (example below from the Page Museum) was an enormous Pleistocene cat that dwarfed the contemporary saber-toothedSmilodon, but it’s relationships have been controversial. Various workers have placed it either close to the African lion (even as a subspecies), while others consider it closer to the jaguar. An interesting aside is that Leigha, in addition to being a graduate student, is also a kindergarten teacher.
Eric Lynch and Blaine Schubert presented preliminary comparisons of the limbs of the giant short-faced bear, Arctodus simus, to other bears in the hope that it may lead to better understanding of A. simus locomotor abilities and, perhaps, feeding style, which has been a point of contention for several years. (Example below also from the Page Museum.)
The technical session concluded with seven posters. I was involved in two of them: in one, Laura Kellam, Vince Schneider and I reported on the current status of the Lake Waccamaw Balaenula skull. There’s not much to add that I haven’t already mentioned in earlier posts on the blog.
Brandi Neifert, DB Poli and I had a poster looking at the rate of tooth breakage in some of the sharks from Carmel Church (specifically Carcharhinus, Galeocerdo, shown below, Physogaleus, and Hemipristis). Our preliminary results suggest that the rate of tooth breakage is the same in all four genera, but the rate of severe breakage (half or more of the crown missing) may be higher in Carcharhinus and Galeocerdo than in the other two genera.
Matthew Mihlbachler, Brian Beatty, Angela Caldera-Siu, Doris Chan, and Richard Lee addressed the difficult issue of observer bias in dental microwear studies. Dental microwear work involves counting and describing the pits and scratches on tooth enamel caused (hopefully) by the diet of whatever the tooth was being used to eat. They found that, even when using a standardized method, different observer got different results, although they tended to identify the same overall trends.
Lindsey Yann, Ryan Haupt, Larisa DeSantis, Jennifer Romer, Sarah Corapi, and David Ettenson examined records of carbon and oxygen isotopes from Pleistocene mammals to compare evaporation sensitivity in various taxa as a proxy for climate. A comparison of these values in different taxa can be used to determine aridity in ancient environments.
Akinobu Watanabe and Gregory Erickson examined bone microstructure in a theropod dinosaur from the Cretaceous of Alaska. Their work suggests that, at least in dinosaurs, bone microstructure has some potential usefulness in making identifications (their specimen appears to be from an ornithomimosaur). In addition, their specimen lacks some features that had previously been suggested as adaptations for a polar environment, throwing that interpretation into question.
Nathan Noll figured fruit pits (endocarps) from Gray Fossil Site. One of the really interesting features on some of these endocarps are the presence of apparent bite marks from squirrels.
Michael Granatosky, Jonathan Bloch, and Richard Hulbert reported a porcupine from the Pliocene of Florida that is unusual in that it had a prehensile tail; the modern North American porcupine lacks this feature.
After the evening banquet, David Steadman wrapped up the meeting with a lecture on fossils from so-called blue holes in the Bahamas. As the Bahamas are made of limestone, they are covered with sinkholes that are filled with fresh water, underlain by opaque, sulfuric acid-rich water, underlain by anoxic salt water. This environment is ideal for preserving fossils, and the sediments in the sides and bottoms of the holes are filled with vast numbers of fossils, including crocodiles, tortoises, and the remains from owl roosts. The Bahamas are located very close to Florida, but separated from the mainland by deep water and swift currents (the Gulf Stream) that presents Florida vertebrates (other than birds and bats) from reaching the islands. Instead, most of the terrestrial vertebrates on the islands come from Cuba.
The fourth meeting of SeAVP was a great success, and everyone’s looking forward to next year’s meeting. I’d like to thank Richard Hulbert, Bruce MacFadden, and the other staff and students of the Florida Museum of Natural History for hosting such a pleasant and successful meeting.