Deinodon horridus, Leidy, 1856

Leidy, J., 1860, Extinct vertebrata from the Judith River and Great Lignite formations of Nebraska., Transactions of the American Philosophical Society 11, pp. 139-154 : 143-145

Deinodon horridus .

In association with the remains of the huge herbivorous Iguanodon , Dr. Mantell found remains of a fit carnivorous cotemporary, the Megalosaurus . This great saurian, named by Dr. Buckland, and first discovered by him in the Oolitic Formation of England, possessed sabre-shaped teeth, with trenchant serrated edges, over three inches in length and an inch in breadth, supported in the jaws by an outer parapet wall, and passing one an other like the blades of scissors.

With the remains of Trachodon , Dr. Hayden likewise discovered those of a representative of the Megalosaurus , to which the name of Deinodon has been applied.

The specimens upon which the latter genus is based, consist of fragments of about a dozen teeth , of which three-fourths are nearly identical in form with those of Megalosaurus , while the others are more or less peculiar. The uniformity in shape of the teeth of Megalosaurus would appear to indicate that the three-fourths of the specimens alluded to, belonged to, at most, another species of the same genus, while the remaining specimens would typify a distinct genus. However, from the variety in form of the latter specimens, together with the fact that all the specimens present the same general appearance, as regards colour, texture, and constitution, I have been induced to regard them as belonging to a single animal, and feel that it must be left for further discovery to ascertain whether such a view is correct.

The teeth of Deinodon , resembling in form those of Megalosaurus , ( figs. 21—34 ,) are laterally compressed conical, with a curvature backward, and with the anterior and posterior borders trenchant and crenated. In transverse section they are quadrately elliptical, with acute poles corresponding with the trenchant edges of the teeth. These specimens, as indicated in figures 25, 29 , are generally worn off at the summits, the borders extending therefrom, and in several instances at the sides. The attrition of the teeth indicates those of the upper and lower jaws to have closed upon one another like the blades of scissors, so that they were well adapted for penetrating, tearing and cutting their animal food.

Of the remaining specimens of teeth, whose form is peculiar in comparison with that of the others, one is the crown of a conical tooth, with feeble lateral compression, and is represented in figures 46, 47 . Its transverse section, ( figure 48 ,) is quadrately rotund, with two acute angles, corresponding with crenated ridges, one of which occupies the inner side of the tooth, while the other is situated postero-externally. The summit of the specimen is worn off in a sloping manner anteriorly. The tooth probably occupied a position in the back of the jaw.

A second specimen, represented in figures 37—40, consists of the greater portion of the crown of a tooth whose transverse section forms the half of an ellipse. The anterior bor­ der is obtusely rounded; the sides are compressed, and the posterior border forms a plane, elevated at the middle and bounded by acute crenated margins. The apex of the tooth is worn off in a sloping manner posteriorly.

A third specimen, represented in figures 35, 36 , consists of a small fragment of a large tooth, like that just described. The latter two specimens perhaps represent canine teeth.

The last of the aberrantly formed specimens, represented in figures 41—45 , consists of the crown of a comparatively small tooth, possessing nearly the shape of the two teeth just mentioned, but its posterior margins are not crenated, and the intervening back surface is more elevated. The apex of the specimen is worn off in a sloping manner anteriorly. This tooth I suspect to represent an incisor.

As the entire dentition of Megalosaurus has not yet been ascertained, it may turn out to be the case, that in other parts of the jaws than those known, it possesses teeth like the ones above described as peculiar. Should on future discovery such a condition of things be proved to exist, Deinodon would then cease to be any thing more than a second species of Megalosaurus .

As anatomical and geological evidence favour the view that Iguanodon , Trachodon , and Hadrosaurus , were amphibious, it is not unlikely that Megalosaurus and Deinodon infested the shores, upon which the former quietly grazed or browsed, and proved to them fierce and destructive enemies. The two carnivorous saurians perhaps held the same office in relation to the more bulky herbivorous lizards, that we find to exist between the larger existing feline animals, and the pachyderm solipedal and ruminant mammals.

Figures

1-20. Trachodon mirabilis 21-48. Deinodon horridus 49-52. Palaeoscincus costatus 53-55. Troodon formosus.