An evolutionary link? Fossil Snake Scan tomorrow!

In this guest post, Brazilian paleontologist Hussam Zaher, professor and curator of the collections of Herpetology and Paleontology at the Museu de Zoologia of the Universidade de São Paulo shares his thoughts on the 50 million year old snake fossil that will be CT scanned tomorrow morning. Starting at 10 am tomorrow, follow the progress of the scan – and the results – on Twitter via @hmns and #snakefossil.

The fossil snake in question is from the Eocene of the Green River Formation in Wyoming and represents the best preserved Caenozoic snake known in a scientific collection in the USA. Our preliminary analysis shows that this snake is closely related to Boavus indelmani, a poorly-known booid snake described in the late 30’s by the paleontologist Charles Gilmore.

The study of this fossil will help better understand the phylogenetic affinities of the Eocene snake genus Boavus. The new fossil also appears to be of critical importance to unveil the evolutionary history of the booid radiation of snakes, a group that includes pythons, boas and their relatives. Indeed it retains a mosaic of primitive and derived skull characters that can be also found in pythons, boas, and a relictual group of New World booids, the tropidophiids, providing an unique opportunity to better understand the evolution of skull features in this group.

The opportunity to study this fossil has been a privilege for me, and I predict it will become central in the debate related to higher-level macrostomatan snake phylogeny and interrelationships. One hot topic in that debate is the evolution of macrostomatan features in higher snakes, i.e., the ability to ingest large prey as a whole. Most macrostomatan features are already present in this exquisite fossil, but some seem to be intermediate between the conditions shown by non-macrostomatan and clearly macrostomatan snake lineages. However, those characteristics are better visualized through CT-scanning, which provides clear and detailed views of the endocranium as well as tridimensional views of all bones that are visible only on the prepared side of the fossil.

Although probably not there, limb vestiges are even more difficult to prepare traditionally, but can be clearly and steadily visualized in a CT-scan. CT imaging will thus help provide a detailed view of the morphology of the skull as well as check for limb vestiges.

Northen water Snake
This Northern water snake (by Carly & Art on Flickr) is not related to the one we’re scanning tomorrow.
We’ll have photos of the fossil and the scanning on Flickr as soon as possible.

Tomorrow at 10 am, the fossil will undergo a 64-slice CT scan at The Methodist Hospital, giving Zaher and the rest of us a peek at the previously-unseen inside and underside. The cross-sectional images will allow him to examine the internal structure of the snake’s brain cavity to more accurately place it within the context of snake evolution.

We’ll be there to bring you the science as it is uncovered, by live tweeting (follow @hmns and #snakefossil) the scanning process on Friday morning. We’ll also be getting behind-the-scenes pictures for our Flickr photostream and a video reaction from Zaher once the fossil has been scanned that we’ll post as soon as we can.

One thought on “An evolutionary link? Fossil Snake Scan tomorrow!

  1. How much information do you know on the, Macrostomatan condition? Some research studies support that; the macrostomatan condition is plesiomorphic for Alethinophidia. How robust is this information, and do you agree based on the findings??

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