Tim and I arrived in Las Vegas last night for the Society of Vertebrate Paleontology meeting. After check-in and picking up name tags, I spent most of the morning catching up with friends and collaborators (this is my first SVP meeting in 3 years, so it’s been awhile in some cases). But I did manage to make it to some talks in the afternoon.
Cathrin Schwartz, Irina Ruf, and Thomas Martin used CT scans to examine the semicircular canals in the ears of squirrels. The semicircular canals in mammalian ears are three tubes connected to the cochlea. The canals are filled with fluid, and pressure variations in the canals are used by the brain to help maintain orientation in 3 dimensions; that’s why it can be difficult to maintain your balance when you have a cold that causes congestion. In squirrels, it turns out that there are differences in the size of the semicircular canals of gliding and arboriality species when compared to fossorial (ground-dwelling) species.
At Tim’s suggestion we attended what turned out to be a remarkable presentation by Alan Shabel on the little-known Congo River clawless otter (Aonyx congicus). He showed video of a captive otter engaged in benthic feeding, pulling worms and other invertebrates from the mud, as well as using its amazingly dexterous fingers to pull snails out of their shells.
Morgan Churchill, Robert Boessenecker, and Mark Clementz examined the relationships of the Otariidae, the sea lions (such as Otaria flavescens, top) and fur seals (such as Callorhinus ursine, below, from the Smithsonian), and specifically what this implies about how they dispersed through the souther hemisphere after apparently originating in the North Pacific.
I spent a lot of time today in the posters. Timothy Cleland reexamined the supposed fossil heart preserved in one specimen of the dinosaur Thescelosaurus, which is on display at the North Carolina Museum of Natural Science (below). Using several lines of evidence, he was able to show that the heart is probably a geologic concretion. Too bad, as the heart made a nice story, but science marches on.
Yasuhisa Nakajima looked at the osteology of limbs in terrestrial and aquatic turtles, and found that the bones tend to be more cancellous (spongy) in aquatic species. This is interesting to me because some marine mammals show an opposite trend in the ribs (less spongy), including sirenians and baleen whales (as Brian Beatty and I showed with Sinistra).
Ryoko Matsumoto suggested that in the Cretaceous and Paleogene crocodilians may have had some competition for the freshwater predator niche from choristoderes, a group of unknown relationships that in many instances converged on crocodilian morphology (below is the choristodere Champsosaurus, from the Mesa Southwest Museum):
Tristan Birkemeier looked at the timing of vertebral suture closure in Allosaurus (such as the example at VMNH, below), something I’ve discussed on the blog before with respect to whales.The patterns of fusion in Allosaurus are quite different in different specimens, which suggests that there could be multiple species lumped together as Allosaurus fragilis.
Sora Kim compared isotope ratios in great white sharks (Carcharodon carcharias) and their apparent ancestor, Cosmopolitodus hastalis (formerly Isurus hastalis; shark taxonomy is in a bit of flux at the moment), especially looking at Peruvian specimens such as the one shown below on exhibit at the Museo de Historia Natural de San Marcos. Carcharodon may have been moving into colder habitats than those preferred by Cosmopolitodus. This could be in part why we very rarely find Carcharodon in the Miocene/Pliocene along the Atlantic coast while Cosmopolitodus is very common; the water along the coast of Virginia and North Carolina was quite warm up to the end of the Miocene at least.
Jingmai O’Connor, Zhonghe Zhou, and Xing Xu reported a remarkable Chinese specimen of the feathered dromaeosaur Microraptor (cast below from the Wyoming Dinosaur Center), which has a wing from an adult enantiornithine bird in its stomach. They suggest that this shows that Microraptor was arboreal, but this might be a bit of overreach; certainly modern birds spend a lot of time on the ground, and the enanornithine could have been caught there. It’s certainly suggestive of arboriality, but not strongly so.
David Rubilar-Rogers and others reported a nearly complete pelagornithid humerus from the Eocene of Antarctica. To review, pelagornithids were huge Eocene-Miocene seabirds with serrated beaks, possibly the largest flying birds ever. The Antarctic humerus is 85 cm long as preserved, but is missing the distal end. As they point out, this is larger than Pelagornis chilensis, the largest well-preserved pelagornithid. I find this especially interesting because we have fragments of pelagornithid humeri from Carmel Church and Mill Pond Creek (Carmel Church example below, compared to a goose), and our fragments appear to be larger than P. chilensis and at least as large as the giant Antarctic specimen.
More talks and posters tomorrow.