GROUP OF SEA-SERPENTS, ELASMOSAUR, AND FISHES.
Fishes, Portheus. Elasmosaurus. Length 50 feet.
Beryx. Clidastes. Length 40 feet.
Osmeroides, etc. Mosasaurus. Length 75 feet.
But the reader inquires, “What is the nature of these creatures thus left stranded a thousand miles from either ocean? How came they in the limestone of Kansas, and were they denizens of land?” These creatures lived in the Cretaceous period. The remains found in this region were mostly those of reptiles and fishes. Thirty-five species of reptiles are known from Kansas alone, representing six orders, and varying in length from ten to eighty feet. One was terrestrial, four were fliers, the rest inhabited the ocean. “When they swam over what are now the plains, the coast-line extended from Arkansas to near Fort Riley, on the Kansas River, and, passing a little eastward, traversed Minnesota to the British possessions, near the head of Lake Superior. The extent of sea to the westward was vast, and geology has not yet laid down its boundary; it was probably a shore now submerged beneath the waters of the North Pacific.”
Other very elongated marine reptiles of this period, but with much thicker bodies, are called, by Professor Cope, Elasmosaurs. In this group, which is not yet fully worked out, occur such genera as Cimoliosaurus, Polycotylus, Polyptychodon, and others. But it seems a pity that they should be in any way separated from the Plesiosaurs, which they strongly resemble (see [chap. iv.], [Plate III.]). Though not sea-serpents, we have introduced them here because they flourished at the same time, and lived in the same seas with the Mosasaurs and other forms of that group. The very large teeth, with strongly marked ridges, of the Polyptychodon are abundant in the Cambridge Greensand that underlies the chalk, and represent a very huge animal.
In our illustration, [Plate XIII.], the artist has represented the Elasmosaurus[37] (of Cope) with its long thin neck stretched out in search of food on the bed of the sea. Professor Cope—thus describing this monster, in language which seems somewhat fanciful—says, "Far out on the expanse of this ancient sea might have been seen a huge snake-like form, which rose above the surface, and stood erect, with tapering throat and arrow-shaped head, or swayed about, describing a circle of twenty feet radius above the water. Then plunging into the depths, naught would be visible but the foam caused by the disappearing mass of life. Should several have appeared together, we can easily imagine tall, flexible forms rising to the height of the masts of a fishing-fleet, or like snakes twisting and knotting themselves together. This extraordinary neck—for such it was—rose from a body of elephantine proportions. The limbs were probably two pairs of paddles, like those of Plesiosaurus, from which this diver chiefly differed in the arrangement of the bones of the breast. In the best-known species twenty-two feet represent the neck in a total length of fifty feet. This is Elasmosaurus platyurus (Cope), a carnivorous sea-reptile, no doubt adapted for deeper waters than many of the others. Like the snake-bird of Florida, it probably often swam many feet below the surface, raising the head to the distant air for breath, then withdrawing it, and exploring the depths forty feet below, without altering the position of its body. From the localities in which the bones have been found in Kansas, it must have wandered far from land; and that many kinds of fishes formed its food is shown by the teeth and scales found in the position of its stomach."
[37] Greek—elasmos, plate; sauros, lizard: probably on account of the shape of the paddles.
But to return to the sea-serpents. Mosasaurus is now known to have been a long slender reptile, with a pair of powerful paddles in front, a moderately long neck, and flat pointed head. The tail was very long—flat and deep—like that of a great eel. Mosasaurus princeps is computed to have been seventy-five to eighty feet long. Clidastes was another genus of long and slender shape, one species of which reached a length of forty feet. Some forms of sea-serpent had sclerotic plates in the eye, such as we found in the fish-lizard, or Ichthyosaurus ([p. 46]), but the announcement that their bodies were protected by bony plates has turned out to be a mistake, and the supposed plates really belonged to the eye.
Leiodon proriger (Cope) was abundant in the old North American Cretaceous sea, and reached a length of seventy-five feet. It had a long projecting muzzle, somewhat like the snout of a sturgeon. Platecarpus and Tylosaurus had peculiarly sharp-pointed heads (see [Fig. 40]).