The Story of the Earth and Man

by Sir John William Dawson

Another strange and monstrous group of creatures, the Elasmosaurs and their allies, combined the long neck of Plesiosaurs with the swimming tail of Ichthyosaurs, the latter enormously elongated, so that these Creatures were sometimes fifty feet in length, and whale-like in the dimensions of their bodies. It is curious that these composite creatures belong to a later period of the Mesozoic than the typical Ichthyosaurs and Plesiosaurs, as if the characters at one time separated in these genera had united in their successors.

One of the relatives of the Plesiosaurs, the Pliosaur, of which genus several species of great size are known perhaps realized in the highest degree possible the idea of a huge marine predaceous reptile. The head in some of the species was eight feet in length, armed with conical teeth a foot long. The neck was not only long, but massive and powerful, the paddles, four in number, were six or seven feet in length and must have urged the vast bulk of the animal, perhaps forty feet in extent, through the water with prodigious speed. The capacious chest and great ribs show a powerful heart and lungs. Imagine such a creature raising its huge head twelve feet or more out of water, and rushing after its prey, impelled with perhaps the most powerful oars ever possessed by any animal. We may be thankful that such monsters, more terrible than even the fabled sea-serpent, are unknown in our days. Buckland, I think, at one time indulged in the jeu d’esprit of supposing an Ichthyosaur lecturing on the human skull. “You will at once perceive,” said the lecturer, “that the skull before us belonged to one of the lower orders of animals. The teeth are very insignificant, the power of the jaws trifling, and altogether it seems wonderful how the creature could have procured food.” We cannot retort on the Ichthyosaur and his contemporaries, for we can see that they were admirably fitted for the work they had in hand; but we can see that had man been so unfortunate as to have lived in their days, he might have been anything but the lord of creation.

But there were sea-serpents as well as other monsters in the Mesozoic seas. Many years ago the Lower Cretaceous beds of St. Peter’s Mount, near Maestricht, afforded a skull three feet in length, of massive proportions, and furnished with strong conical teeth, to which the name Mosasaurus Camperi was given. The skull and other parts of the skeleton found with it, were held to indicate a large aquatic reptile, but its precise position in its class was long a subject of dispute. Faujas held it to be a crocodile; Camper, Cuvier, and Owen regarded it as a gigantic lizard. More recently, additional specimens, especially those found in the Cretaceous formations of North America, have thrown new light upon its structure, and have shown it to present a singular combination of the character of serpents, lizards, and of the great sea saurians already referred to. Some parts of the head and the articulation of the jaws, in important points resemble those of serpents, while in other respects the head is that of a gigantic lizard. The body and tail are greatly lengthened out, having more than a hundred vertebral joints, and in one of the larger species attaining the length of eighty feet. The trunk itself is much elongated, and with ribs like those of a snake. There are no walking feet, but a pair of fins or paddles like those of Ichthyosaurus. Cope, who has described these great creatures as they occur in the Cretaceous of the United States, thus sketches the Mosasaur: “It was a long and slender reptile, with a pair of powerful paddles in front, a moderately long neck, and flat pointed head. The very long tail was flat and deep, like that of a great eel, forming a powerful propeller. The arches of the vertebral column were more extensively interlocked than in any other reptiles except the snakes. In the related genus Clidastes this structure is as fully developed as in the serpents, so that we can picture to ourselves its well-known consequences; their rapid progress through the water by lateral undulations, their lithe motions on the land, the rapid stroke, the ready coil, or the elevation of the head and vertebral column, literally a living pillar, towering above the waves or the thickets of the shore swamps.” As in serpents, the mouth was wide in its gape, and the lower jaw capable of a certain separation from the skull to admit of swallowing large prey. Besides this the lower jaw had an additional peculiarity, seen in some snakes, namely, a joint in the middle of the jaw enabling its sides to expand, so that the food might be swallowed “between the branches of the jaw.” Perhaps no creatures more fully realize in their enormous length and terrible powers the great Tanninim (the stretched-out or extended reptiles) of the fifth day of the Mosaic record, than the Mosasaurus and Elasmosaurus. When Mr. Cope showed me, a few years ago, a nearly complete skeleton of Elasmosaurus, which for want of space he had stretched on a gallery along two sides of a large room, I could not help suggesting to him that the name of the creature should be Teinosaurus[AF] instead of that which he had given. Marsh has recently ascertained that the Mosasaurs were covered in part at least with bony scales.

[AF] Heb. Tanan; Gr. Teino, Tanuo; Sansc. Tanu; Lat. Tendo.—Ges. Lex.

LIFE IN THE MESOZOIC PERIOD.

Aquatic Reptiles and Cephalopods. Reptiles.—Plesiosaur and Osteopygis, Ichthyosaur, Teliosaur, Plesiosaur, Elasmosaur, Mosasaur (in order of the heads from left to right).—Cephalopods.—Ammonite, Crioceras, Belemnites, Baculites, and Ammonites (in order from left to right). The Reptiles after Hawkins and Cope’s Restorations.

These animals may serve as specimens of the reptilian giants of the Mesozoic seas; but before leaving them we must at least invite attention to the remarkable fact that they were contemporary with species which represent the more common aquatic reptiles of the modern world. In other words, the monsters which we have described existed over and above a far more abundant population of crocodiles and turtles than the modern waters can boast. The crocodiles were represented both in Europe and America by numerous and large species, most of them with long snouts like the modern Gavials, a few with broad heads like those of the alligators. The turtles again presented not only many species, but most of the aquatic subdivisions of the group known in modern times, as for instance the Emydes or ordinary fresh-water forms, the snapping turtles, and the soft-shelled turtles. Cope says that the Cretaceous of New Jersey alone affords twenty species, one of them a snapping turtle six feet in length. Owen records above a dozen large species from the Upper Mesozoic of England, and dates the first appearance of the turtles in England about the time of the Portland stone, or in the upper half of the Mesozoic; but footprints supposed to be those of turtles are found as far back as the Trias. Perhaps no type of modern reptiles is more curiously specialized than these animals, yet we thus find them contemporaneous with many generalized types, and entering into existence perhaps as soon as they. The turtles did not culminate in the Mesozoic, but go on to be represented by more numerous and larger species in the Tertiary and Modern. In the case of the crocodiles, while they attained perhaps a maximum toward the end of the Mesozoic, it was in a peculiar form. The crocodiles of this old time had vertebrae with a hollow at each end like the fishes, or with a projection in the front. At the end of the Mesozoic this was changed, and they assumed a better-knit back, with joints having a ball behind and a socket in front. In the Cretaceous age, species having these two kinds of backbone were contemporaneous. Perhaps this improvement in the crocodilian back had something to do with the persistence of this type after so many others of the sea-lizards of the Mesozoic had passed away.