Sthenodectes, Gregory 1912

Mader, Bryn J., 2008, A species level revision of Bridgerian and Uintan brontotheres (Mammalia, Perissodactyla) exclusive of Palaeosyops, Zootaxa 1837 (1), pp. 1-85 : 72

Genus STHENODECTES Gregory 1912

Age. Uintan.

Subage. Early Uintan.

Type species. S. incisivum ( Douglass 1909) .

Included species. Genus is monospecific.

Diagnosis. Large-sized (average length P2 to M 3 in CM 2398 is 195 mm) brontothere with six very large, spatulate upper incisors and a very long, pointed canine.

Discussion. The type skull of Sthenodectes incisivum ( Fig. 25 ) was described in 1909 by Douglass who provisionally identified it as a new species of Telmatherium , T. incisivum . Despite this identification, Douglass believed that the skull probably represented a genus distinct from Telmatherium but preferred not to create a new generic name at that time. In 1912, W.K. Gregory also concluded that the specimen was generically distinct from Telmatherium and proposed for it the new generic name Sthenodectes .

Wilson (1977) named a new species of Sthenodectes , S. australis , based on a skull (TMM 41723-3) from the Pruett Formation (now the Devil's Graveyard Formation) of Texas. Mader (1989), however, concluded that Sthenodectes australis is not referable to this genus at all, but rather is a diplacodont similar to Protitanotherium . Mader also stated that the exact generic assignment of " Sthenodectes " australis is unclear and that it could represent an entirely new genus (see the Discussion section of the present paper for Protitanotherium ).

Sthenodectes is known from only two or three skulls and, given the extremely small sample size, statistical analysis is not practical at this time. All of these skulls are very imperfectly preserved, but they appear to be very similar in morphology. At present, therefore, there is no basis for the recognition of more than one species.

Figures

FIGURE 25. Holotype skull of Sthenodectes incisivum (CM 2398) in A, ventral; B, dorsal; and C, lateral views. Areas shaded gray are reconstructed. After Osborn, 1929.