Deinodon horridus Leidy, 1856

Sahni, Ashok, 1972, The vertebrate Fauna of the Judith River formation, Montana, Bulletin of the American Museum of Natural History 147 (6), pp. 319-416 : 358

Deinodon horridus Leidy, 1856

Deinodon horridus LEIDY, 1856 , p. 72 .

Aublysodon mirandus LEIDY, 1868, p. 198 .

Aublysodon lateralis COPE, 1876b, p. 248 .

Laelaps incrassatus COPE, 1876a, p. 248 ; 1876b, p. 341 .

Laelaps hazenianus COPE, 1876b, p. 343 .

Ornithomimus grandis MARSH, 1890 , p. 85 .

Dryptosaurus kenabekides HAY, 1899, p. 348 .

Gorgosaurus libratus LAMBE, 1914, p. 13 .

Deinodon horridus was proposed by Leidy (1856) for about a dozen teeth collected by Hayden from the Judith River Formation. This species was the first of the carnivorous dinosaurs to be recovered from the Upper Cretaceous sediments of the American continent. The collection of teeth on which the genus was based consists of two distinct morphological types, although Leidy (1856, p. 73; 1860, p. 144) considered them as belonging to a single species. Leidy (1860, p. 145) correctly guessed that the differences involved in the two groups of teeth were positional in nature and suggested that the teeth with U-shaped cross sections were incisors. Later, Leidy (1868, p. 198) erected a separate genus, Aublysodon , for the inclusion of those teeth he had earlier regarded as incisors. These teeth have serrated crests on the posterior side. Cope (1876a, 1876b) described a number of species from the Judith River Formation under the genus Laelaps , the type of which is L. aquilunguis , obtained from New Jersey. The genus Aublysodon was placed in synonymy with Deinodon by Matthew and Brown (1922). Of the three species of Laelaps collected from the Judith River Formation, two, L. explanatus and L. falculus , were referred to Dromaeosaurus and the other, L. incrassatus , was transferred to Deinodon by Matthew and Brown (1922).

On the basis of the dentition it is not possible to separate the closely related genera Gorgosaurus and Deinodon . As suggested by a number of authors including Matthew and Brown (1922, p. 383), and Russell (1964, p. 13), the genus Gorgosaurus is probably synonymous with the Judith River Formation Deinodon . Lambe (1914) described G. libratus from the Oldman Formation and then restudied it in greater detail (Lambe, 1917) on the basis of more complete material than that known for Deinodon . The name Deinodon , however, has priority and no differences can be shown to exist between the type specimen of Deinodon and material of Gorgosaurus . The name Deinodon should be retained for the large carnivorous dinosaur found in the Judith River and Oldman formations.

The present collection consists of a number of teeth similar to those described by Leidy (1856) and later figured by him ( Leidy, 1860, pl. 9, figs. 21-48) . AMNH 8513 is a large saber-shaped linguolabially compressed tooth. Both its anterior and posterior edges are serrated. It is either a maxilla or dentary tooth ( fig. 8M, N ). The premaxillary teeth are small with a Ushaped cross section. Morphologically similar, but larger, teeth come from the anterior part of the dentary. The premaxillary teeth ( AMNH 8514 , fig. 8Q, R ) are usually smaller than the anterior dentary teeth ( AMNH 8515 , fig. 80, P ) and have serrated crests lateral to the apex of the tooth that become more posterior toward the base of the tooth. A strong median keel is present that is not found in the larger dentary teeth.

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The type specimen of Ornithomimus grandis Marsh (1890) was supposedly recovered from the Eagle Sandstone, but probably came from the Judith River Formation, and was referred by Gilmore (1920) to Deinodon .

Figures

FIG. 8. A. Chamops segnis. AMNH 8486, labial view of left dentary. B. Lingual view. Both x 5. C. AMNH 8488, lingual view of left maxilla. D. Labial view. Both x 5. E. cf. Xenosauridae, AMNH 8498, labial view of left maxilla. F. Lingual view. Both x 5. G. Peltosaurus piger, AMNH 8495, lingual view of left maxilla, x 5. H. AMNH 8494, lingual view of right dentary, x 5. I. Paraderma bogerti, AMNH 8504, lingual view of right maxilla. x 5. J. Parasaniwa wyomingensis, AMNH 8499, lingual view of left dentary, x 5. K. Leptochamops denticulatus, AMNH 8491, lingual view of right maxilla, x 5. L. Exostinus lancensis, AMNH 8497, lingual view of right maxilla, x 5. M. Deinodon horridus, AMNH 8513, posterior view of isolated tooth. N. Lateral view. Both x 13. 0. AMNH 8515, lateral view of anterior dentary tooth. P. Posterior view. Both x 13. Q. AMNH 8514, posterior view of?premaxillary tooth. R. Lateral view. Both x 12. S. Paronychodon lacustris, AMNH 8522, lingual view of isolated tooth. T. Labial view. Both x 12. U. Kritosaurus cf. K. breviceps, AMNH 8525, lateral view of isolated tooth. V. Posterior view. Both x 1 2. W. Procheneosaurus altidens, AMNH 8527, labial view of isolated tooth. X. Anterior or posterior view. Both x 12. Y, Z.?Sebecosuchia, AMNH 8549, views of an solated tooth. Both x 10.

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