Just this last week I was thinking to myself ‘gee, wouldn’t it be nice if I would look at a disarticulated amphisbaenid braincase’ and wouldn’t you know it, a paper came out this month on that very thing. Not only that, but there are movies of each of the elements at digimorph. Every once in a while the paleontology gods favor me I guess. Now if only I could find out why scolacophidians are considered basal beyond the absence of a crista circumfenestralis I’d be pretty set.
On a related note, I read an interesting paper about all of the various snakes with hind limbs and it got me to thinking. Why haven’t I ever heard of Eupodophis descouensi (Rage and Escuillie 2000) before? And why isn’t Pachyophis woodwardi (Nopcsa, 1923) x-rayed or ct scanned to find out if it had hind limbs? It seems like Pachyophis would be a pretty good candidate for that sort of thing. I know that there’s an articulated specimen of Palaeophis out there somewhere. Why hasn’t a museum or university snatched that up for study?
However, beyond frustrating me with what hasn’t been done, the paper brought up the issue of pachyostosis which is a character that I now find rather interesting. All of these snakes that certainly do or possibly have hind limbs show pachyostosis of the dorsal vertebrae and ribs, about where the lung would have been. Do modern sea snakes show a similar feature? How about snakes that go swimming regularly but are considered terrestrial? The two hypotheses for why this character existed were for either increased erythrocyte production (indicating greater lung capacity or oxygen requirements as for diving) or for ballast to compensate for the levity of the lung in water. Personally I think that it would be a combination of the two. As a snake lineage gets into the habit of diving or staying submerged for prolonged periods, it’d need greater lung capacity (and thicker blood to carry the oxygen) but it would also need to compensate for that increased buoyancy by adding weight to the ribs and vertebrae, which it was doing anyway.
Monday, January 17, 2005
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