Fig. 150.—a, Skull of Labyrinthodon Jœgeri, much reduced in size; b, Tooth of the same. Trias Württemberg. of three feet in length and two feet in breadth. Restorations of some of these extraordinary creatures have been attempted in the guise of colossal Frogs; but they must in reality have more closely resembled huge Newts.
Remains of Reptiles are very abundant in Triassic deposits, and belong to very varied types. The most marked feature, in fact, connected with the Vertebrate fauna of the Trias, and of the Secondary rocks in general, is the great abundance of Reptilian life. Hence the Secondary period is often spoken of as the "Age of Reptiles." Many of the Triassic reptiles depart widely in their structure from any with which we are acquainted as existing on the earth at the present day, and it is only possible here to briefly note some of the more important of these ancient forms. Amongst the group of the Lizards (Lacertilia), represented by Protorosaurus in the older Permian strata, three types more or less certainly referable to this order may be mentioned. One of these is a small reptile which was found many years ago in sandstones near Elgin, in Scotland, and which excited special interest at the time in consequence of the fact that the strata in question were believed to belong to the Old Red Sandstone formation. It is, however, now certain that the Elgin sandstones which contain Telerpeton Elginense, as this reptile is termed, are really to be regarded as of Triassic age. By Professor Huxley, Telerpeton is regarded as a Lizard, which cannot be considered as "in any sense a less perfectly-organised creature than the Gecko, whose swift and noiseless run over walls and ceilings surprises the traveller in climates warmer than our own." The "Elgin Sandstones" have also yielded another Lizard, which was originally described by Professor Huxley under the name of Hyperodapedon, the remains of the same genus having been subsequently discovered in Triassic strata in India and South Africa. The Lizards of this group must therefore have at one time enjoyed a very wide distribution over the globe; and the living Sphenodon of New Zealand is believed by Professor Huxley to be the nearest living ally of this family. The Hyperodapedon of the Elgin Sandstones was about six feet in length, with limbs adapted for terrestrial progression, but with the bodies of the vertebræ slightly biconcave, and having two rows of palatal teeth, which become worn down to the bone in old age. Lastly, the curious Rhynchosaurus of the Trias is also referred, by the eminent comparative anatomist above mentioned, to the order of the Lizards. In this singular reptile
Fig. 151.—Skull of Rhynchosaurus articeps. Trias. (After Owen.) (fig. 151) the skull is somewhat bird-like, and the jaws appear to have been destitute of teeth, and to have been encased in a horny sheath like the beak of a Turtle or a Bird. It is possible, however, that the palate was furnished with teeth.
The group of the Crocodiles and Alligators (Crocadilia), distinguished by the fact that the teeth are implanted in distinct sockets and the skin more or less extensively provided with bony plates, is represented in the Triassic rocks by the Stagonolepis of the Elgin Sandstones. The so-called "Thecodont" reptiles (such as Belodon, Thecodontosaurus, and Palœosaurus, fig. 152, c, d, e) are also nearly related to the Crocodiles, though it is doubtful if they should be absolutely referred to this group. In these reptiles, the teeth are implanted in distinct sockets in the jaws, their crowns being more or less compressed and pointed, "with trenchant and finely serrate margins" (Owen). The bodies of the vertebræ are hollowed out at both ends, but the limbs appear to be adapted for progression on the land. The genus Belodon (fig. 152, c) is known to occur in the Keuper of Germany and in America; and Palœosaurus (fig. 153. e) has also been found in the Trias of the same region. Teeth of the latter, however, are found, along with remains of Thecodontosaurus (fig. 153, d), in a singular magnesian conglomerate near Bristol, which was originally believed to be of Permian age, but which appears to be undoubtedly Triassic.
| Fig. 152.—Triassic Reptiles. a, Skull of Nothosaurus mirabilis, reduced in size—Muschelkalk, Germany; b, Tooth of Simosaurus Gaillardoti, of the natural size—Muschelkalk, Germany; c, Tooth of Beladon Carolinensis—Trias, America; d, Tooth of Thecodontosaurus antiquus, slightly enlarged—Britain; e, Tooth of Palœosaurus platyodon, of the natural size—Britain. |
The Trias has also yielded the remains of the great marine reptiles which are often spoken of collectively as the "Enaliosaurians" or "Sea-lizards," and which will be more particularly spoken of in treating of the Jurassic period, of which they are more especially characteristic. In all these reptiles the limbs are flattened out, the digits being enclosed in a continuous skin, thus forming powerful swimming-paddles, resembling the "flippers" of the Whales and Dolphins both in their general structure and in function. The tail is also long, and adapted to act as a swimming-organ; and there can be no doubt but that these extraordinary and often colossal reptiles frequented the sea, and only occasionally came to the land. The Triassic Enaliosaurs belong to a group of which the later genus Plesiosaurus is the type (the Sauropterygia). One of the best known of the Triassic genera is Nothosaurus (fig. 152, a), in which the neck was long and bird-like, the jaws being immensely elongated, and carrying numerous powerful conical teeth implanted in distinct sockets. The teeth in Simosaurus (152, b) are of a similar nature; but the orbits are of enormous size, indicating eyes of corresponding dimensions, and perhaps pointing to the nocturnal habits of the animal. In the singular Placodus, again, the teeth are in distinct sockets, but resemble those of many fishes in being rounded and obtuse (fig. 153), forming
Fig. 153.—Under surface of the upper jaw and palate of Placodus gigas. Muschelkalk, Germany. broad crushing plates adapted for the comminution of shell-fish. There is a row of these teeth all round the upper jaw proper, and a double series on the palate, but the lower jaw has only a single row of teeth. Placodus is found in the Muschelkalk, and the characters of its dental apparatus indicate that it was much more peaceful in its habits than its associates the Nothosaur and Simosaur.