The Fourth Annual Meeting of the Southeastern Association of Vertebrate Paleontology got underway this morning with a full schedule of talks.
Bruce MacFadden started things off with a review of the FLMNH contributions to vertebrate paleontology over the last 50 years. With almost 1000 fossil localities spanning about 40 million years, Florida has produced huge numbers of specimens that have contributed to understanding paleobiology, especially in the Caribbean region. Just as one stand-out example, the McGehee Farm Site produced some of the first evidence that South American mammals began reaching North America as long as 8.5 million years ago (ground sloth Eremotherium eomigrans from FLMNH shown above).
We don’t get a lot of dinosaur talks at SeAVP, but this year Gregory Erickson and Mark Norell discussed the detailed structure of hadrosaur teeth. Hadrosaurs unusual among dinosaurs in having complex grinding dental batteries. Even so, it has long been thought that structurally their teeth were much more simple than in mammals, consisting of only two types of tissue. Erickson and Norell’s detailed examination of tooth sections indicate that they’re much more complex (six different tissue types). Interestingly, it seems that with increased grinding, rather than making the enamel thicker they hardened some of dentine to perform the same function. Moreover, the hundreds of teeth in a hadrosaur’s mouth were held together with cementum, so that the tooth battery functioned kind of like a single large mammal molar. Finally, difference in the relative amounts of the tissues suggest that different hadrosaur groups were specialized for different types of feeding, such as the Lambeosaurus and Parasaurolophus shown below (both from the Canadian Museum of Nature).
David Moscato discussed an apparently new glyptosaurine lizard from San Diego. Glyptosaurines are armored lizards which are related to living alligator lizards (like Dracaena paraguayensis, below, from the Tennessee Aquarium) among others. The San Diego specimen is still imbedded in sediment, and David is using CT scans to plan the preparation of the specimen. An interesting side light of this is the apparent desiccation cracks that show up on several bedding surfaces in the block of sediment.
Brian Beatty and Matthew Mihlbachler looked at changes in mesowear (large-scale wear patterns) in Florida horses over time. Horse tooth morphology and carbon isotope work both suggest that horses generally shifted toward eating more grasses over time. Brian’s and Matt’s work reinforces this, with more recent horses showing heavier tooth wear, indicating a more abrasive diet (grasses are very abrasive). Interestingly, though, other Florida herbivores such as bison, camels, and rhinoceroses don’t show such a dramatic shift toward more abrasive diets.
Carly Manz, Emily Woodruff, and Aldo Rincón compared isotopes from tooth enamel from three early Miocene sites in Florida and Panama. Specifically they looked at C12/C13 ratios, which can help distinguish between C3 and C4 vegetation, and O16/O18 ratios, which can be affected by various climate features, including temperature. Carbon ratios between Florida and Panama were essentially the same, suggesting similar vegetation. However, the oxygen ratios were quite different, suggesting somewhat more variable environmental conditions than what are seen between Florida and Panama today.
Continuing the Panama theme, Aldo Rincón and Jonathan Bloch reported on two new camels from Panama. They’re from the subfamily Floridatragulinae, a fascinating group of camels known only from relatively tropical areas such as as Florida and Mexico (and now Panama). The Panamanian species are the oldest and apparently most primitive members of the subfamily.
Christina Byrd presented her senior thesis work (with me and Rowan Lockwood) on the taphonomy of whale vertebrae from Carmel Church. Christina spent last summer measuring 288 whale vertebrae from Carmel Church to look for any patterns in the style or likelihood of preservation. Some of the results were expected; for example, the vertebrae tend to be better preserved if both epiphyses are fused to the centrum. Others were unexpected and a bit surprising. We have twice as many atlases (1st neck vertebrae) as axes (2nd neck vertebrae), even though we should have the same number of each. It’s also noteworthy that more than 20% of the vertebrae in the sample were part of articulated or associated skeletons (such as the Eobalaenoptera “Caroline” shown below), an amazingly high percentage for a bone bed like Carmel Church.
Blaine Schubert, Steven Wallace, and Jim Mead presented an update of the activities at the Gray Fossil Site in Tennessee, which I’ve talked about in earlier posts. The biggest news from Gray is the acquisition of adjacent property that greatly increases the size of the site. They’re also constructing a new education center.
Jim Mead, Blaine Schubert, Steven Wallace, and Sandra Swift presented on specimens of the delightfully named Monstersauria from Gray Fossil Site. The monstersaurians are armored lizards that include the modern Gila monster Heloderma suspectum (below, from the Nashville Zoo), which they have highly distinctive osteoderms (armor plates).
Alex Hastings and Jonathan Bloch looked at new primitive caimans from Panama. Caimans were in both South America and Wyoming in the Eocene, but by the Oligocene they were gone from North America, replaced by the related alligators. Through most of the rest of the Cenozoic caimans diversified in South America while alligators did the same in North America (with one group reaching China!), but over the last few million years caimans again made it into Central/North America (Paleosuchus palpebrosus, below, from the Nashville Zoo, is a South American form). This is some rather complex biogeography, and the Panamanian forms may shed some light on it.
Steven Jasinski addressed the complex problems associated with defining and identifying different fossil genera of river turtles, especially Trachemys (such as the example from Gray Fossil Site, below). Most molecular studies find the different species to be closely related, but morphological data, especially when fossils are considered, are much less consistent.