Dwarf pipesnakes

One group of intrepid researchers, led by David Gower at the Natural History Museum in London, recently tried to extract DNA from three Anomochilus leonardi, with mixed success. Two of these were preserved over 50 years prior, and no genes could be recovered from their tissues. From one specimen collected in 2003, partial sequences of 12S and 16S rRNA mitochondrial genes were amplified, for a total of 221 informative sites. In their trees, Anomochilus leonardi formed a clade with Cylindrophis maculatus, rendering the latter's family, Cylindrophiidae, paraphyletic. However, this conclusion is based on limited data, and this study was done before the discovery of A. monticola, from which fresh tissue could presumably be obtained.

As early as 1890, van Lithe de Jeude noticed the similarities and differences between Anomochilus and other basal alethinophidians. He remarked that it was similar to Anilius scytale, a primitive snake from the Amazon rain forest, in that both lacked a mental groove (a structure on the chin that allows the lower jaw to open widely), but that the scalation of the head was more similar to Cylindrophis than Anilius. Respectively, Anilius, Anomochilus, and Cylindrophis are known as the red, dwarf, and Asian pipesnakes, and they were once treated as a single family together with shield-tailed (uropeltid) and sunbeam snakes (look out for future articles!), though today these are referred to separate families. In outward appearance, all of these snakes are have glossy scales, a result of their scale microornamentation, and a pattern of yellow or white spots and a red tail band against a dark ground color. They have blunt tails and few specialized head scales, with mostly undifferentiated ventrals. These basal lineages have much to teach us about snake evolution, if we can find enough of them to learn from!

Scanning electron microscope photograph of ventral scale microornamentation of Anomochilus leonardi: BMNH 1946.1.17.4

Despite all the mystery, we do know some intriguing things about anomochilids. Unlike some basal snakes, but like others, Anomochilus has no pelvic girdle vestiges. However, it does possess vestiges of pectoral girdle muscle, unusual among snakes, which lack any vestige of a pectoral girdle bone. In addition, Anomochilus is unique in having lost the left lung entirely, a structure which is vestigial, but still present, in most other snakes. Like other basal snakes, Anomochilus has only a few teeth - 3 in each upper jaw and 5 in each lower jaw. What they eat is a matter of pure speculation, as are most details about how they reproduce (one female specimen contained four eggs, so we know that they are probably all oviparous, with small clutch sizes). Most of these basal alethinophidians eat elongate vertebrates, such as caecilians, amphisbaenians, and other snakes, because they do not have sufficiently flexible skulls to consume the very large prey items eaten by the macrostomate snakes (boas, pythons, and caenophidians).

ACKNOWLEDGMENTS

I would like to thank exactly no photographers, because apparently no one has ever taken a picture of these things, except for Das et al., who thoughtfully published photos of the type specimen of Anomochilus monticola in 2008.

REFERENCES