05 July 2012

Fossil Vertebrate of the Month: Rutiodon carolinensis

At the end of last month, I spent a week out East, visiting the collections at the American Museum of Natural History and in Chapel Hill at a workshop that I would recommend to any geologists out there that are in the late stages of a PhD or the early stages of a postdoc.  While the two states have followed very different historical trajectories, to vertebrate paleontologists New York and North Carolina have one big thing in common.  The Newark Supergroup is a series of Late Triassic and Early Jurassic formations that run from Nova Scotia to the Carolinas; representing a wet, seasonal rift valley environment, these rocks are among the best places in the world to find fossils from early in the "Age of Dinosaurs" (and certainly the best in North America outside of the red beds of the Southwest).  Pictured above is perhaps the most iconic fossil from the Newark Supergroup, the phytosaur Rutiodon carolinensis.  Any student that's ever taken a class from me will be familiar with phytosaurs, which are one of my favorite examples of convergent evolution.  Superficially, members of this now-extinct group were very similar to modern crocodiles and doubtless filled a similar ecological niche (piscivores/ambush predators).  However, several features of the skeleton show that they are not the direct ancestors of crocodiles (which, in the Triassic, were primarily small, agile, and land-living); the most notable of these is the placement of the nostrils above the eyes rather than at the end of the snout as is the case in alligators and crocodiles.  The specimen pictured above is a historically significant one.  As the species name suggests, the first Rutiodon specimens to be uncovered were found in North Carolina.  One of these specimens, from a coal mine near the town of Egypt, was acquired by W.D. Matthew in 1895.  He brought it back to New York, where it became the first vertebrate fossil in the collection of the American Museum of Natural History (it bears the specimen number AMNH 1), which in the subsequent decades would grow to become the largest collection of fossil vertebrates in the world.

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