The first leads to snake-like creatures, destitute of limbs, and which must have been functionally the representatives of the serpents in the Palæozoic, though batrachian in their affinities ([Fig. 135]). They are found both in Europe and America; and Huxley describes one from Ireland more than twenty-one inches long, and with over one hundred vertebræ.[57] Some extraordinary traces are found on the sandstones of the coal-formation,[58] which appear to indicate that there may have been species of this type much larger than any represented by skeletons, and with bodies perhaps six inches in diameter. It is not unlikely that they had the habits of the modern water snakes.
Fig. 136.—A large Carboniferous Labyrinthodont (Baphetes planiceps, Owen).
a, Anterior part of the skull, viewed from beneath. One-sixth natural size, b, One of the largest teeth, natural size.
A second line leads upward to large crocodile-like creatures, with formidable teeth, strong bony armour, and well-developed limbs (Labyrinthodontia, [Figs. 136, 137]). Some of them must have attained a length of ten feet. They were lizard-like in form, could walk well, as is seen from the footprints of some of the species which present a considerable stride, and moved over mud without the belly touching the ground. Their tails were long, and probably useful in swimming. Their heads were flat and massive, and their teeth were strengthened by a remarkable folding inward of the outer plate of enamel ([Fig. 137] b). The belly was protected by bony plates and closely imbricated scales. In some of the species at least the upper parts were clothed with horny scales, and the throat and sides were ornamented with pendent scaly fringes or lappets.[59] Their general aspect and mode of life must have resembled those of modern alligators; and in the vast swamps of the Coal-period, full of ponds and sluggish streams swarming with fish, they must have found a most suitable abode. While rigid anatomy may ally these animals rather with the batrachians than the true reptiles, it is evident that their great size, their capacity for walking with the body borne well above the ground, their bony and scaly armour, their powerful teeth and their capacious chests, with well-developed ribs, indicate conditions of respiration and general vitality quite comparable with those of the highest modern members of the class Reptilia.
Fig. 137.—Baphetes planiceps (Owen).
a, Fragment of maxillary bone showing sculpture, four outer teeth, and one inner tooth. Natural size. b, Section of inner tooth. Magnified, c, Dermal scale. Natural size.