SEBECOSUCHIA

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 : 351

SUBORDER? SEBECOSUCHIA

Figure 8Y, Z

AMNH 8549 represents another rare group which is tentatively assigned to the Sebecosuchia (fig. 8Y, Z). Sebecosuchian teeth resemble theropod teeth as pointed out by Simpson (1937a, 1937b) and Colbert (1946), and were consistently confused as such by earlier workers. Such teeth differ from contemporary theropod teeth in that the blade is usually straighter, the serrations on the anterior and the posterior sides are finer, and a more prominent groove is present along the midline of the tooth on the lingual and labial side.

Similar teeth have been reported from the Milk River Formation of Alberta ( Russell, 1935, p. 123, fig. 9) and from the Lance Formation of Wyoming ( Estes, 1964, p. 143). They have yet to be reported, however, from the Judith River Formation or from its equivalent formation in Alberta.

Russell (1935) suggested that the teeth may have come from the premaxilla of a deinodont. Considering the known skulls of these large carnivores, this seems unlikely. Estes (1964, p. 143), on the other hand, believed it probable that the teeth represent a juvenile theropod. At present, there is no conclusive evidence that the teeth belong to the theropods, or, for that matter, to the Saurischia .

Langston (1956) reviewed criteria useful in distinguishing between sebecid teeth and carnosaur teeth.

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.