Bulletin of the American Museum of Natural History, 21: 259–265. 1905. Article XIV.
By Henry Fairfield Osborn.
In 1902, the American Museum expedition in Montana, led by Mr. Barnum Brown, and accompanied by Professor R. S. Lull, secured considerable portions of the skeleton of one of the great Carnivorous Dinosaurs of Upper Cretaceous or Laramie age. Additional portions of this skeleton (Amer. Mus. No. 973) are now (1905) being taken out. I propose to make this animal the type of the new genus Tyrannosaurus, in reference to the size, which greatly exceeds that of any carnivorous land animal hitherto described.
I also briefly characterize as Dynamosaurus another carnivorous dinosaur, with dermal plates, found by Mr. Brown in 1900. The carnivorous group has hitherto been considered as belonging to the single genus Dryptosaurus, but it is probably little less diversified than its herbivorous contemporaries among the Iguanodontia and Ceratopsia. The generic distinctions which are herein indicated by partially studied remains will probably be intensified by future research. Geological, geographical, and morphological considerations render it a priori probable not only that the above genera as well as Deinodon are distinct from Dryptosaurus but that a fifth Cretaceous genus of somewhat more primitive character, which may be called Albertosaurus, is represented in the British Columbia skulls hitherto described as Dryptosaurus.
I. Nomenclature.
A revision of the names which have been applied to the Carnivorous Dinosaurs of the Cretaceous appears to be necessary.
In 1856, Deinodon horridus, from the Judith River Beds of Montana, was securely[259] 1 founded by Leidy[259] 2 on Megalosaurian teeth, and those first mentioned and first figured in Leidy's original description and memoir (see citation below, p. 261) on the Judith River Vertebrates must be regarded as valid types.
In 1868, the genus Aublysodon Leidy was based (1) on large serrate incisor teeth, truncate posteriorly, which probably belong in the anterior part[260] 1 of the jaw of some species of Deinodon, (2) on smaller, non-serrate teeth, also truncate posteriorly, which probably do not belong with Deinodon. Since the teeth first mentioned (1) may belong to Deinodon the name Aublysodon is probably invalid.
In 1866 Lælaps aquilunguis Cope[260] 2 from the Cretaceous Greensand of New Jersey, was distinguished from Deinodon Leidy by the characters of the teeth.
In 1877, Marsh[260] 3 pointed out that the name Lælaps was preoccupied by Koch, and proposed to replace it by Dryptosaurus.
The genus Dryptosaurus Marsh was therefore founded upon the type of Dryptosaurus aquilunguis (Cope) from the Cretaceous Greensand of New Jersey.
In 1876, Cope described the species Lælaps incrassatus from the Judith River Beds of Montana,[260] 4 and in the same communication the species Aublysodon lateralis, Lælaps explanatus, Lælaps falculus. He subsequently[260] 5 described from the same beds the additional species Lælaps hazenianus, L. cristatus, L. lavifrons.
In 1892,[260] 6 Cope described two skulls from the uppermost (true Laramie) beds of the Cretaceous system, Edmonton series, of Alberta, identifying them with L. incrassatus. These skulls have recently[260] 7, [260] 8 been more fully described and figured by Lambe as Dryptosaurus incrassatus.
The geological distribution has a very important bearing on this matter of nomenclature. Since Hayden's original description (1857) the position of the Judith River Beds has been confirmed by Hatcher and Stanton as belonging to a lower horizon than the true Laramie Series, namely to the Ft. Pierre, and since all the Ceratopsia from the Judith River Beds belong to older and simpler forms than the Ceratopsia of the Laramie and Montana beds, it is highly probable that the reference by Cope and Lambe of the Edmonton Carnivore to a New Jersey Cretaceous genus, Dryptosaurus, and to a Judith River species (D. incrassatus), is incorrect.
It appears certain that the Edmonton and Laramie carnivores are generically distinct from those of the Judith River Beds.
[p. 259] 1 It should be stated that both Professor Cope and Dr. Hay have advanced the contrary view very strongly that Leidy's type of Deinodon is indefinite and the name invalid.Back
[p. 259] 2Proc. Acad. Nat. Sci. Phila., VIII, p. 72.Back
[p. 260] 1A complete jaw of Allosaurus in the American Museum shows that the front teeth are truncate posteriorly as in the type of Aublysodon.Back
[p. 260] 2Proc. Acad. Nat. Sci. Phila., Aug., 1866, p. 276.Back
[p. 260] 3"This name Lælaps is preoccupied, having been used by Koch in 1835, and again by Walker in 1843. It may, therefore, be replaced by Dryptosaurus. This genus is allied to Megalosaurus, and is represented in American Cretaceous strata by several species, among them Dryptosaurus aquilunguis" ('Notice of a New and Gigantic Dinosaur,' Amer. Jour. of Sci. and Arts, Vol. XIX, July, 1877, p. 88).Back
[p. 260] 4Proc. Acad. Nat. Sci. Phila., Oct., 1876, pp. 248–340.Back
[p. 260] 5Proc. Acad. Nat. Sci. Phila., 1876, p. 343.Back
[p. 260] 6Cope, Proc. Amer. Philos. Soc., Vol. XXX., 1892, p. 240.Back
[p. 260] 7Ottawa Naturalist, Vol. XVII, pp. 133–139, Nov., 1903.Back
[p. 260] 8Contributions to Canadian Palæontology, Vol. III (quarto), Part III, pp. 1–27, pll. i–vii.Back