The earliest group of lepospondyls, the ai'stopods, were, interestingly, the most specialized of all amphibians. They first appeared in the Early Carboniferous (Mississippian) — about 20 million years after the first amphibians, the ichthyostegalians, had set foot on land (see p. 52). Presumably the ai'stopods evolved from a 4-legged ancestor, but almost immediately they lost their legs, and became snakelike, burrowing amphibians.
Obviously, this specialized way of life had its advantages, since the ai'stopods were a long-lived group, surviving for almost 80 million years, until the middle of the Permian period.
name: Ophiderpeton time: Late Carboniferous locality: Europe (Czechoslovakia)
and North America (Ohio) size: 28 in/70 cm long About 230 vertebrae made up the elongated body of this snakelike a'istopod. There is no trace of limbs or limb girdles within the skeleton. The eyes were quite large, and placed well forward on the skull, which was about 6 in/15 cm long. The structure of the skull was similar to that of a primitive labyrinthodont, although paleontologists can find no definite connection between these 2 groups.
Ophiderpeton must have led the life of a burrower. Certainly, this lifestyle would have paid dividends during the Late Carboniferous, when vast amounts of rotting vegetation were accumulating on the forest floor and in the swamps — the coal beds of today. All kinds of insects, worms, centipedes, snails and other invertebrates would have lived and fed on this débris, and provided the burrowing ai'stopods with a rich source of food.
name: Phlegethontia time: Late Carboniferous to Early Permian locality: Europe (Czechoslovakia)
and North America (Ohio) size: 3 ft 3 in/1 m long
Although Phlegethontia had the same snakelike body as that of Ophiderpeton (above), and presumably led a similar burrowing life, its skull was quite different in structure. Large openings, separated by narrow bones, made it a lightweight structure (fenestrated like that of a modern snake).
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