A third species is the formidable "estuarine" crocodile, which frequents the tidal portions of rivers from the Bay of Bengal to China and Australia. It exceeds all of its race in stature, usually exceeding twenty feet long, and one old specimen on record was thirty-three feet from tip to tip. It is held in great fear by fishermen, for in many cases it develops man-eater proclivities, and has all the ferocity and resourcefulness of its Nilotic cousin. The salt-water habitat of this species recalls the fact that among the many kinds of fossil crocodilians known, from the Lias onward, one was a purely marine form.
The crocodiles are followed in the classification of the reptiles by several extinct groups, known only as fossils of the Mesozoic Age. The first of these is the subclass Plesiosauria, containing a series of predatory creatures characterized by very long necks, short tails, and feet that in the older forms indicate a terrestrial existence, but later exhibit a progressive change to paddles, showing that finally the plesiosaurs were wholly aquatic. This was accompanied by a steady increase in size, until finally a length of at least forty-five feet was reached—chiefly by extension of the neck—in the elasmosaurus of the Cretaceous rocks of Kansas.
Another subclass, Ichthyosauria, restricted to the Mesozoic Age, were large, swimming, marine "fish lizards" with a somewhat whalelike form, the front limbs transformed into paddles, and the snout in the form of a long bill filled with sharp teeth. They lived on fishes, cuttlefish, mollusks, etc., and had the general habits of sharks. They died out early in the Cretaceous epoch, and left no descendants.
A third extinct subclass is that of the pterodactyls, or "flying dragons" (Pterosauria), which possessed the air throughout the Mesozoic Age, and filled the place of birds in the fauna of that period, although they had no relationship to the real birds that came later. Some were no larger than sparrows, but later ones spread their leathery wings twenty feet or more. The origin and real affinities of these winged reptiles are unknown and they left no descendants.
We find in the Cretaceous formations skeletons of very long, slender marine reptiles (Pythonomorpha) with a lizardlike head and all four limbs in the form of paddles, of which the mososaurs are the best known. These were the latest of the Mesozoic reptiles; and about the time of their disappearance we begin to find the earliest fossil suggestions of the subclass Sauria which contains our modern orders Lacertilia, the lizards, and Ophidia, the serpents. Neither of these owe their ancestry to any of the fossil groups just mentioned, in spite of superficial resemblances, but "their origin has probably to be looked for among the Prosauria, of which Sphenodon (the tuatara, [see page 183]) is the only surviving member." They are also very distinct from crocodiles in structure.
| MESOZOIC FLYING REPTILE (PTERODACTYL) |
| (Restoration, after Owen) |
LIZARDS AND CHAMELEONS—TURNCOATS OF THE WOODS
Lizards (Lacertilia) are creatures of hot climates, and especially of deserts, and they exhibit an almost endless variety of shape, size, structure, and adaptations to their surroundings and a mode of life that is primarily dictated by their food. The majority are terrestrial, but some species are semiaquatic. There are climbing, swiftly running, and even flying forms, while others lead a subterranean life like earthworms. Most of them subsist on animal food, varying from tiny insects and worms to birds and mammals, while others live upon a vegetable diet.
Lizards, like snakes, have a scaly skin covered with a thin, horny pellicle which is shed from time to time, flaking off in pieces except in the wormlike species, where it is sloughed whole as by snakes. In most lizards the scales are well developed, and "shingle" the back and sides of the body, but in some they are like little tubercles, giving a granular appearance—a good example of which is the "Gila monster" of Arizona. Lizards are, as a rule, adaptively colored according to their habitat, so that browns and grays prevail in the sand-running species or those, like the monitors and iguanas, that are mostly aquatic; but brilliant hues in varied, even fantastic, patterns adorn many of the small, agile, tropical kinds, whose safety lies in their swiftness of movement and cleverness in hiding. This is supplemented in most species by the capability of changing color, a faculty that is most serviceable in the chameleons, by rendering them more or less invisible to the hawks and other animals that try to catch and eat them. Some of the more sluggish, earth-dwelling kinds are further protected by many spines sprouting from the skin, as is familiar in our western "horned toad," and in the fearsome-looking "moloch" of Australia; and the iguanas are provided with an erectile spiny crest along the ridge of their backs, most notable in the basilisks.