Fig. 141.—Arm of Proterosaurus Speneri. Reduced. Permian.
But the great Mesozoic reptiles were not fully enthroned, till the Permian, an unsettled and disturbed age, characterised by great earth movements, had passed away, and until that period of continental elevation, with local deserts and desiccation, and much volcanic action, which we call the Trias, had also passed.
Then in the Jurassic and early Cretaceous the reptiles culminated, and presented features of magnitude and structural complexity unrivalled in later times. At the same time the Labyrinthodonts disappear, or are degraded into the humble stations which the modern Batrachians now occupy.
To understand the reptiles of this age, it will be necessary to notice the subdivisions of their modern representatives. The true reptiles now existing constitute the following orders:—1, the Turtles and Tortoises (Chelonia); 2, the Snakes (Ophidia); 3, the Lizards (Lacertilia); 4, the Crocodiles and Alligators (Crocodilia). All of these, except the snakes, are well represented among Mesozoic fossils; but we have in this middle age of the earth’s geological history to add to them from five to seven orders now altogether extinct, and these not of low and inferior organisation, but including species far in advance of any now existing both in elevation and magnitude, and constituting the veritable aristocracy of the reptile race. It will best serve our purpose here to consider chiefly these perished orders and their history, and then to notice very shortly those that now survive.
Fig. 142.—Skeleton of Ichthyosaurus. Lias. England.
The first of the extinct orders is that of the great Sea-lizards,[65] of which the now familiar Ichthyosaurus and Plesiosaurus of the English seas, to be seen in all museums and text-books, are the types ([Figs. 142, 142a] and 142b). These were marine animals of large size, but not fishes or amphibians. They were true air-breathing reptiles, but with paddles for swimming instead of feet, and some of them with long flattened tails for steering and propulsion. They bore, in short, precisely the same relation to the other members of the class Reptilia which the Whales and Porpoises bear to the ordinary quadrupeds. Some of these animals are believed to have been fifty or sixty feet in length, thus rivalling the Whales, while others were of smaller dimensions, like the Porpoises and Dolphins. Some, like the Ichthyosaurus and Pliosaurus ([Fig. 142]a), were strongly built and powerful swimmers, and able to destroy the largest fishes, while others, like Plesiosaurus, had the body short and compact, the head small, and the neck long and flexible, and probably preyed on small animals near the borders of the waters. Catalogues of British fossils alone include about thirty species of Enaliosaurs, which haunted the coasts of Mesozoic Europe, a wonderful fact, when we consider the absence of these creatures from the modern seas, and the probability that only a fraction of the species are yet known to us.