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. Snakes

It is a well-known fact that snakes are reptiles, members of the class Reptilia. Within the Reptilia we find four orders: Testudines (turtles & tortoises); Crocodylia (crocodiles, alligators, and the gavial); Rhynchocephalia (the lizard-like Tuatara of New Zealand, comprising just one living species); and the Squamata (lizards, amphisbaenians, and snakes). Snakes form the suborder Serpentes within the order Squamata, which they share with two other suborders, the Lacertilia (lizards) and the Amphisbaenia (amphisbaenians).

The Squamata is by far the greatest reptilian order, containing about 5 800 living species, including some 3 000 lizard species, about 130 amphisbaenian species, and approximately . . . 2 700 snake species.

It is generally accepted that snakes evolved from lizards, but any direct connection is yet to be discovered. The term “missing link” is especially significant when applied to snake phylogeny, as only a few fossil snake genera have been found and no species intermediate to lizards have been discovered. One fairly plausible theory is that snakes evolved from burrowing lizards that first lost their limbs, external ears, and, almost, their eyesight.

During the burrowing period, the unique sense of prey detection, using the forked tongue and the Jacobson’s organ and possibly the beginning of heat reception pits in some species, began to develop. Eventually certain species again ventured onto land surface, the lidless eyes redeveloped, but external ears and limbs were lost forever (though some of the more primitive snake families still possess vestigial pelvic girdles), being replaced by other sophisticated means of hearing and locomotion.

All this, of course, would have taken millions of years. Today we still have burrowing snakes, legless amphisbaenians that possess some characteristics of both lizards and snakes, and many legless lizards; what we do have is a concrete link between the suborders. Snake evolution for the time being still remains a partial mystery.