The Fossil Reptiles of New Jersey
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By Prof. E. D. Cope
(Continued from Vol. I, page 30.)
While grim and monstrous Dinosaurs ranged the forests and flats of the coast of the Cretaceous sea, and myriads of Gavials basked on the bars and hugged the shores, other races peopled the waters. The gigantic Mosasaurus, the longest of known reptiles, had few rivals in the ocean. These Pythonomorphs were the sea-serpents of that age, and their snaky forms and gaping jaws rest on better evidence than he of Nahant can yet produce.
Ten species of this group are known from the Cretaceous beds of the United States, of which six have been found in New Jersey. Two others occur in Europe. In relative abundance of individuals, as well as of species, New Jersey is much in advance of any other part of the world where excavations have been made.
These creatures have been referred to the neighborhood of the Varanidæ or Lace-lizards, which now haunt the shores of rivers in the tropics and southern regions of the Old World. Cuvier, Owen and others, have expressed this view, and there has been little dissent from it expressed by palæontologists. They readily constitute, however, a distinct order of reptiles, combining features of serpents, lizards, and Plesiosaurians. This is readily understood by the light of the abundant material discovered in various parts of the United States. The lizard-like affinities are, it is true, to the Varanians rather than to any others.
The Mosasaurus was a long 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 interlocked more extensively than in other reptiles except the snakes, presenting in a prolongation of the front of one, which enters beneath that immediately in advance of it, a rudiment of that extra articulation called the "zygosphenal." 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 land; the rapid stroke; the ready coil; or the elevation of the head and vertebral column, literally a living pillar towering above waves or brush of the shore swamps. While the construction of the skull was as light as that of the serpents, it was, apparently, not so strong. The sutures are more frequently of the squamosal type, and the brain case was not as fully ossified in front. The teeth, too, are less acute, and therefore less adapted for retaining struggling prey. While the jaws were longer, the gape was not so extensive as in serpents of the higher groups, for the os quadratum, the suspensor of the lower jaw, though equally movable and fastened to widely spread supports, was much shorter than in them. But there was a remarkable arrangement to obviate any inconvenience arising from these points. While the branches of the under jaw had no sutural connection, and possessed independent motion, as in all serpents, they had the additional peculiarity, not known elsewhere among vertebrates (except in a few snakes), of a movable articulation a little behind the middle of each. Its direction being oblique, the flexure was outwards and a little downwards, greatly expanding the width of the space between them, and allowing their tips to close a little. A loose flexible pouchlike throat would then receive the entire prey, swallowed between the branches of the jaw; the necessity of holding it long in the teeth, or of passing it between the short quadrate bones would not exist. Of course the glottis and tongue would be forwards. The physiognomy of the reptile, with apparently dislocated jaws and swollen throat, as he passed a Chimæra to his internal laboratory, could scarcely be prepossessing.
“Literally a living pillar towering above the waves”
The Clidastes and Macrosaurus were the more slender of these heteroclite beings, while Mosasaurus embraces the most gigantic. The Clidastes iguanavus could not have been shorter than thirty feet, and presented a reduction of the length of the paddles, consistent with its thoroughly serpent-like vertebral column. Macrosaurus validus considerably exceeded this length. Mosasaurus Mitchellii and M. Missuriensis propelled sixty feet of length through the waves, while no portion of these have been found equal to the M. maximus, which have recently been exhumed.
The reptilian whales of those troublous times, were the Cimoliasaurs and Elasmosaurs. These were the Plesiosaurs of Cretaceous life, and probably had a great range over the earth. Portions of them have been found in England and North America to our far western regions. Cimoliasaurus appears to have resembled Plesiosaurus in general, while Elasmosaurus added to its type an enormous and flattened tail, relatively as long as that of the Mosasaur, or the modern Iguana, but not so flat as in the former; perhaps it were more as in the Crocodile as to compression, while relatively still longer. But both of these types present one strange feature. The processes which connect the arches of the vertebræ, are related to each other in directions the reverse of that which prevails along vertebrata generally, being perhaps the same as the zygosphen of the serpent and Clidastes, without the usual accompaniment. But the more probably explanation is, that they are the usual "zygapophyses" with the articular facets somewhat altered in direction. They are very oblique, turned a little over from the perpendicular, which latter position is sometimes more or less approached by these processes in other animals.
“The bulk was whale-like, the neck long and flexible, while short paddles and the serpent-like tail, sped this most colossal of our sea-saurians on his destructive career.”
The Elasmosaurus orientalis rests on the evidence of but few remains, but these are like those of its better known congener E. platyurus. The vertebræ are nearly as large as those of an elephant, and indicate a totally different type of reptile from the Mosasaurus. The bulk was whale-like, the neck long and flexible, while short paddles and the serpent-like tail, sped this most colossal of our sea-saurians on his destructive career. The skull was light, and with a long narrow, and very flat muzzle; the nostrils or spout-holes were near the orbits; the teeth long and cylindric, and much sharper than those of Mosasaurus. The most ravenous fish—the Enchodi, or great barracudas of the Cretaceous, were his food, and few we might suppose could escape the plunge from the elevated position whence he scanned the waters for prey. Cimoliasaurus magnus is more abundant in New Jersey. In bulk it was little inferior to the last, but it was apparently abbreviated and depressed behind, and so must have presented a very peculiar form. Precisely what that was and whether it supported a caudal fluke, we must determine hereafter. Elasmosaurus platyurus was forty-five feet in length.
While the crocodiles are most numerous in individuals in the deposits of this period, the turtles exceed them and all other orders in number of species. There have been twenty found in the Cretaceous of New Jersey, and three additional ones are known from the Tertiaries of the same State. The Cretaceous turtles may be arranged under four heads, viz., true Emydes or fresh water forms; Chelydrine Emydes, or snappers; Trionychidæ or soft shells; and Hydraspididæ, a type now confined to the Southern Hemisphere, which throw the head round the side of the shell, instead of drawing it in. It will be observed that all of these forms occur at the present day in fresh water only, and that true marine turtles are not found in this part of the Cretaceous formation. Add to this the fact that the crocodiles are rather estuary and river animals; that the Dinosaurs are terrestrial; and that by far the most abundant shells of the same region are oysters and Exogyræ, and we have indicated a condition of occasional separation from the high ocean, by seaward bars and islands, or even by occasional considerable strips of dry land.
The Emydiform turtles all belong to the genus Adocus of Cope, and were often of the size of our large gulf species, but generally of far more massive structure. The snapper-like forms are more numerous; they have been taken to be marine types, and indeed their fore-limbs appear to have been more paddle like than those of the species in modern rivers. They are represented by nine species, which pertain to five genera. These forms differ much in the relative union of the shield of the carapace, and its marginal pieces. In the genus Peritresius of Cope, the margin was largely separate, and the shell covered by a thin skin; in Lytoloma Cope the margin was also distinct, except in front and rear, and the carapace was covered by heavier shell-like dermal plates. Propleura Cope contained one large species—P. sopita, where the margin was broad and flat, and free as in the last, except that it had a broad union with the disc in front. Finally Osteopygis Cope, was solidly knit fore and aft by suture between disc and margin. Of its three species, O. chelydrinus presented sharp points round the circumference, like a snapping tortoise. O. emarginatus had open notches between, at the same parts of the margin, and O. platylomus was even. O. emarginatus was the giant of all the snappers and probably commonly reached a length of six feet. An ally, the Euclastes platyops, whose cranium has been found, presented a broad, massive palatal surface, apparently for crushing, rather than the sharp edges and hooked bill of the raptorial snapper. It may have crushed shells for food. The Lytoloma angusta Cope shows a similar type of jaws. In the Euclastes, the skull measures about a foot in length, and eight inches in width, and accommodated immense temporal muscles, which indicate the power of its bite.
More elegance and less strength characterize the Hydraspid species. Five of these have been described, as follows: Bothremys Cookii Leidy; Prochonias sulcatas Leidy sp.; P. strenuus Cope; P. princeps Cope, and Taphrosphys molops Cope.
In the first we have a well protected cranium with small eyes, with the Milesian traits of a broad mouth, a pug-nose, and a stiff upper lip. His form seems to combine the capacities of doing as much injury to others and receiving as little himself as possible. What his shell was we do not know, but we know that he could not draw his head into it, by reason of a peculiar structure on the sides of his inner nostril. Of the other genera, the numerous shell fragments tell a similar story. It is only necessary to see whether the pelvis was attached to the lower shell, or a horizontal curve and turn round outside, as a goose rests its head above its wing. Or, if the front part of the plastron only be found, if there be a supplemental plate in the front, we know both the flexure of the neck, the arrangement of the pelvis, and the structure of the nose. Such is a result of the law of correlation, which holds through long series of forms, but must be carefully modified for other series, and in some points cannot be read at all.
In Prochonias, as in the modern genus of Brazil, Hydromedusa, the ileum is fastened by a great suture to the shell above, right on the line of junction of two rib bones. But the bones of the front of the carapace, are quite different from those of Hydromedusa. In Taphrosphys the structure is more powerful. The rib bones are united into one, and rise up round the sutural scar; leaving it at the bottom of a deep pit. T. molops was a powerful swimmer and perhaps what he lost in mass, was gained in speed. Many shells of both this genus and the last, are sculptured with netted grooves (P. sulcatus and P. strenuus) or ribbed lines (P. princeps, and T. molops), and they were probably covered with a thin skin instead of dermal scales. P. princeps was large and massive, equalling some of the snappers.
The more beautifully marked "soft-shelled" forms, the Tryoniches, are represented by three species. Their position shows that they lived at an earlier period than in Europe. The Trionyx of our Miocene (T. lima Cope) was large and rough, with narrow sharp ridges. Its remains occur with Dolphins and Porpoises, but it may have been floated or washed from the mouth of a fresh-water stream into such strange company.
The Crocodiles of the modern period are characterized by the hollow crowns of their teeth, and one genus of the Cretaceous, viz., Bottosaurus Aggasiz, possesses a similar dentition. Most of the Miocene species of both Europe and America possess, on the contrary, solid crowns, composed of closely concentric cones, as we see in the Mosasaurus and some other reptiles. Some of them have been on this account mistaken for Mosasauroids, but none of the latter are known above the Cretaceous. In this country the Miocene forms of this kind are gavials, of even larger size than those of the Cretaceous. The belong to the genus Thecachampsa Cope, of which T. sericodon was first discovered by Dr. H. C. Wood in Southern New Jersey, and T. sicaria by Philip T. Tyson in Southern Maryland. In both localities their remains are mingled with those of Dolphins and Whales, and their carcases have all floated together on the ocean currents and tides to their present resting places. In Europe there are some species of the same genus, while allies of the true crocodilian form represent the Pleurodon of Meyer. The gavials of the Cretaceous present a similar character of teeth, and approach remarkably near to the Thecachampsæ, when we consider the great hiatus between the life of the two great periods in other departments. The gavials of the Miocene differ in but a few important points from the Thoracosauri of the Cretaceous. The latter were very numerous in individuals, and appear under five specific forms.
In the plate accompanying this article, the artist has attempted an ideal representation of a few of the subjects which haunted the shores of our country, when our prairies were the ocean bottom, and our southern and eastern borders were far beneath the Atlantic. Lælaps aquilunguis occupies the foreground on a promontory, where his progress is interrupted by the earnest protest of an Elasmosaurus. Mosasaurus watches at a distance with much curiosity and little good will, while Osteopygis views at a safe distance the unwonted spectacle. On the distant shore a pair of the huge Hadrosauri browse on the vegetation, squatting on their haunches and limbs as on a tripod. Thoracosaurus crawls up the banks with a fish, and is ready to disappear in the thicket.