Deinodon horridus (Leidy, 1856)

Matthew, W. D., & Brown, B., 1922, The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta., Bulletin of the American Museum of Natural History 56, pp. 365-385 : 382-383

Deinodon Leidy, 1856 , had for genotype

D. horridus

of the Judith River, Montana. This was the first genus of the Upper Cretaceous carnivorous dinosaurs to be described. It is based upon a number of more or less fragmentary teeth, figured by Leidy in his memoir on the Judith River. Leidy originally regarded them as all belonging to the same species, but subsequently adopted Cope’s suggestion that those of U-shaped cross-section were of a different genus, which Leidy named Aublysodon . Cope rejected the name “ Dinodon ” as a homonym of Dinodus -which it is not; the derivation of the two words is different—and proposed Laelaps , which is a preoccupied name, for the lenticular or ovalsectioned teeth, with L. aquilungius of New Jersey as type. Marsh substituted Dryptosaurus for the preoccupied name Laelaps and added a couple more species of “ Aublysodon " in 1892. Hay in 1899 pointed out that Cope had restricted the name Deinodon to the U-shaped teeth before Leidy gave the name Aublysodon to these teeth. Aublysodon therefore, cannot be applied to these teeth. Since it now appears that both types of teeth belonged to one animal, this all becomes unimportant and needs no further discussion.

The original idea of Leidy was that the U-shaped teeth were in the front of the jaw. Cope, however, believed that the lower jaw of his L. aquilunguis did not have that kind of teeth in front, hence the conclusion, shared by Leidy and Marsh, that the U-shaped teeth were a distinct type. When Marsh secured complete skulls of megalosaurians from the Morrison, it was evident that the upper front teeth approached this type to some degree, but they are by no means so sharply contrasted in size and form with the maxillary and dentary teeth as are the teeth of Deinodon . Marsh as late as 1892 regarded them as distinct.

Skulls from the Edmonton of Canada were described by Cope in 1892 and subsequently more fully described by Lambe in 1904, but these still failed to show the characters of the premaxillary teeth. In 1905 Osborn described the gigantic Tyrannosaurus and “ Dynamosaurus ” of the Lance and distinguished them primarily by large humerus ascribed to the one and dermal plates to the other.1 Osborn in this paper excludes from “ Deinodon ” the small U-shaped teeth figured by Leidy, but recognizes the large U-shaped teeth as “premaxillary and premandibular.” Lambe in describing Gorgosaurus follows Osborn in this restriction and distinguishes Gorgosaurus from Deinodon by the possession in the premaxilla of just such teeth as are thus excluded from the type of Deinodon ! The fact is, of course, that the “ Gorgosaurus ” skulls from the Red Deer River show that the large U-shaped teeth are anterior dentary, the small U-shaped teeth premaxillary, and the oval and compressed teeth posterior maxillary and mandibular teeth of the same genus, just as Leidy provisionally regarded them in his original description of Deinodon .

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There is, therefore, nothing in the dentition to separate Gorgosaurus from Deinodon and they are unquestionably nearly related and, so far as the teeth are concerned, would appear to be the same genus. But, pending the discovery of adequate topotypes from the Judith River beds, the identity has not been finally and conclusively proven. There may be differences in the skull. Certainly, in comparison with the very distinct generic differences that separate both from Tyrannosaurus , they fall very clearly into the same group..

Marsh’s name Dryptosaurus may in an equally provisional way be retained for the New Jersey Cretaceous D. aquilunguis . Laelaps must be abandoned as a preoccupied name, Aublysodon as a synonym of Deinodon .

Osborn has already (1917) called attention to another fragmentary type, Manospondylus gigas , as possibly identical with Tyrannosaurus but based upon an inadequate type. It may further be noted that Marsh described the feet of Tyrannosaurus and its allies, referring them to Ornithomimus under the name of O. grandis. The type of this species is from the Judith, and is probably correctly referred by Gilmore (1920, p. 122) to Deinodon . Referred specimens from the Lance are more probably Tyrannosaurus , as referred by Gilmore (loc. tit.).

Cope referred to “ Laelaps ” and “ Aublysodon ” a number of quite small species known only from isolated teeth, some of which probably belong to the genus here described.

Figures

Fig. 1. Type skull of Dromaeoaaurus albertensis, one-half natural size.