Reptile & Amphibian Forums

Those who are interested in the origin of snakes may be interested in the following paper:

http://www.kingsnake.com/aho/pdf/menu3/rickshine/originofsnakes.pdf

This paper investigates eye anatomy and found that snake eyes share many characteristics with those of aquatic vertebrates, suggesting and corroborating earlier phyologenetic analyses and fossil data linking snakes with marine reptiles called mossasaurs. The oldest known snake fossils had legs, and they were marine animals. These snakes also had the macrostomatan condition. Therefore the microstomatan snakes likely evolved their fixed jaws and small gapes secondarily from a macrostomatan condition. Indeed, detailed investigations of different microstomatan snakes show that their jaws are highly speciliazed and differ markedly from those of lizards, and therefore supportively of derived, rather than primitive conditions. Snakes therefore appeared to have evolved in the marine environment and the blind and burrowing snakes evolved later from marine ancestors.

Good paper. It added another perspective, but did not help with snakes relationship to everything else. Finding out that scolecophidia may not be the most primitive is interesting. This is going to give me something to talk about with my classmates and professor, thank you.
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-Bradley

>>Good paper. It added another perspective, but did not help with snakes relationship to everything else. Finding out that scolecophidia may not be the most primitive is interesting. This is going to give me something to talk about with my classmates and professor, thank you.
>>-----
>>-Bradley

Quite the contrary. The eye anatomy is another nail in the coffin of the burrowing origin of snakes. Since the oldest known snakes, with legs, are of marine origin, one must look naturally at marine reptiles as the possible ancestor of snakes. The marine mosasauroid lizards, closely allied to the monitor lizards, are perfectly positioned as the prime candidates for snake ancestor.

If you do not mind me asking, how many "nails" are there? I do remember one of the many squamata clades having snakes and mosasaurs together, but then with a "?" in another. What other papers would you suggest reading?

I have also heard that some genetic data has snakes closest to Lacertiforms.... I need to find that source though...
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-Bradley

>>If you do not mind me asking, how many "nails" are there? I do remember one of the many squamata clades having snakes and mosasaurs together, but then with a "?" in another. What other papers would you suggest reading?
>>
>>I have also heard that some genetic data has snakes closest to Lacertiforms.... I need to find that source though...
>>-----
>>-Bradley

Yes indeed, some DNA studies find snakes closest to the Iguanians. Here is an example:

TED M. TOWNSEND,ALLAN LARSON, EDWARD LOUIS, AND J. ROBERT MACEY 2004. Molecular Phylogenetics of Squamata: The Position of Snakes, Amphisbaenians, and Dibamids, and the Root of the Squamate Tree. Syst. Biol. 53(5):735–757

These authors found that "Snakes are grouped with iguanians, lacertiforms, and anguimorphs, but are not nested within anguimorphs."

However, a more recent paper, based on highly reliable SINE data, shows that anguimorph lizards is the sister group of snakes. See fig. 4 in the link below:
Sauria SINEs: Novel Short Interspersed Retroposable Elements That Are Widespread in Reptile Genomes