Fig. 40.—Snout of Tylosaurus. (After Marsh.)
A few words may be added here with regard to Professor Cope’s important discovery of Leiodon—a genus already alluded to as having been founded by Sir Richard Owen. The type specimen of Leiodon dyseplor,[38] which first indicated the characters of this wonderful species, was obtained from the yellow beds of the Niobrara epoch of the Jornada del Muerto, near Fort McRae, New Mexico. The greater part of the remains have been described by Professor Leidy. But a second specimen, more complete in all respects, was discovered by Professor Cope’s exploring party during an expedition from Fort Wallace, Kansas, in 1871. This specimen he has fully described and figured in the report already referred to ([p. 140]). It is a very instructive specimen, including fifty of the vertebræ from all parts of the vertebral column, a large part of the cranium, with teeth, as well as important limb-bones. These precious relics were excavated from a chalk “bluff,” or high bank. Fragments of the jaws were seen lying on the slope, and other portions entered the shale. On being followed, a part of the skull was taken from beneath the roots of a bush, and the vertebræ and limb-bones were found farther in. The series of vertebræ, after extending some way along the face of the bluff, finally turned into the hill, and were followed as far as time would permit, but part of the tail series had to be left. In size, the vertebræ of this enormous sea-serpent exceed those of Mosasaurus brumbyi. The latter has hitherto been the largest known species of the order of Pythonomorphs, exceeding twofold in its measurements the M. giganteus of Belgium. So the present reptile is much larger in its dimensions than the New Jersey species called maximus by Professor Cope. “If, as appears certain,” says the professor, “the Mosasauroid discovered by Webb measures seventy-five feet in length, and the M. maximus measured eighty, the Leiodon dyspelor must have been the longest reptile known, and approaches very nearly the extreme of the mammalian growth seen in the whales, though, of course, without their bulk. Such monsters may well excite our surprise, as well as our curiosity, in the inquiry as to their source of food-supply, and what the character of those contemporary animals preserved in the same geologic horizon.”
[38] We retain the old spelling with the e as being nearer to the Greek, although Professor Cope writes it “Liodon.”
In our illustration, [Plate XIII.], the artist has endeavoured to realise the outward aspect of the two genera of sea-serpents, Mosasaurus and Clidastes. The fishes which they are pursuing are well-known genera from the English Chalk, such as Beryx.
Ten species of Clidastes have been unearthed from the Kansas strata. They did not reach such a size as the Leiodons, but were of elegant and flexible build, the largest species, C. cineriarum, reaching a length of forty feet (see [Fig. 41]). A smaller species, of elegant proportions, has been called C. tortor (Cope). Its slenderness of body was remarkable, and the large head was long and lance-shaped. Its lithe movements doubtless helped it to secure many fishes. It was found coiled up beneath a ledge of rock, with its skull lying undisturbed in the centre.
The accounts given by Professor Cope of his explorations and the difficulties encountered in procuring the valuable specimens on which his conclusions are based, are most interesting, and such as every fossil-hunter will appreciate. We, in England, who visit clay pits, stone quarries, railway cuttings, etc., during a morning or an afternoon walk, and return home at our leisure with a few small specimens in our pockets, or in a bag at our back, can hardly realise how arduous must be the work of finding, digging out, and transporting for such long distances the remains of the monsters of Kansas and other parts of North America.
The following extracts have been selected from Professor Cope’s report, with a view to illustrating the nature of the explorations undertaken. “The circumstances attending the discovery of one of these will always be a pleasant recollection to the writer. A part of the face, with teeth, was observed projecting from the side of a bluff by a companion in exploration, Lieutenant James H. Whitten, United States Army, and we at once proceeded to follow up the indication with knives and picks. Soon the lower jaws were uncovered, with their glistening teeth, and then the vertebræ and ribs. Our delight was at its height when the bones of the pelvis and part of the hind limb were laid bare, for they had never been seen before in the species, and scarcely in the order. While lying on the bottom of the Cretaceous sea, the carcase had been dragged hither and thither by the sharks and other rapacious animals, and the parts of the skeleton were displaced and gathered into a small area. The massive tail stretched away into the bluff, and, after much laborious excavation, we left a portion of it to more persevering explorers.”