Tuesday, June 10, 2008

Thecodontosaurus antiquus

This is my attempt at a reconstruction of Thecodontosaurus antiquus. No one really knows what the skull looked like except for a juvenile of a closely-related southern Welsh species Pantydraco caducus (formerly known as Thecodontosaurus caducus) so I pretty much made it up - loosely basing it on Benton et al. (2000). The interesting thing about Theco is that there are so many postcranial jumbled together that no one has any idea what the forelimb to hindlimb ratio is. I attempted a lower fore-hind limb ratio - so as to make it look like Theco is actually not obligatory bipedally nor quadrupedally, basically facultative.

Thecodontosaurus was discovered in 1834 at the Durdham Down in Clifton, Bristol, UK and is the fourth dinosaur to be named. It is also the oldest dinosaur from Britain at 203-215 million years old. The original Clifton materials were destroyed in the second world war when a bomb hit the Bristol City Museum. However, some elements, including a braincase, had fortunately escaped destruction as they had been taken back to the United States by Othniel Marsh as part of a collections exchange with the Yale University Museum in the late 19th century.

Most of the more recent studies on Theco have been conducted on materials collected from a cave deposit in a quarry in Tytherington, just north of Bristol, in the 1970s. Over the course of the next few decades, numerous specimens (at least from 30 or so individuals) were prepared out, but the University of Bristol has just under 6 tons of bone-bearing rocks still awaiting preparation.

Recent work suggests that Bristol and its surrounding areas, including south Wales where Pantydraco lived, were a series of tropical islands - in which case, Pantydraco may just be another island species of Thecodontosaurus.


Zach said...

Where does Thecodontosaurus shake out in terms of saurischian phylogeny? I've read varying accounts, everything from a fairly general prosauropod to a basal prosauropod to a basal SAUROPOD to a basal sauropodmorph.

I also read that Thecodontosaurus may be an insular dwarf, which is kind of cool.

Mambo-Bob said...

Hi Zach,

According to Yates (2003), theco is supposed to be a very basal sauropodomorph with only Saturnalia being more basal.

And yes, I think it is a fascinating idea that theco may be an insular dwarf. I don't think there were anything much bigger than theco around the Bristol area anyway...