Thescelosaurus, Gilmore, 1913

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 : 361

Thescelosaurus cf. T. neglectus Gilmore, 1913

Figure 9E, F

The material, consisting of about 12 teeth from the Judith River Formation, is the first record of the genus from the Campanian of the

North American continent. Gilmore (1913, 1915), described T. neglectus from the Lance Formation of Wyoming. Later Parks (1926) described in detail the skeleton of T. warreni from the Edmonton Formation of Alberta. Sternberg (1937) erected a new genus, Parkosaurus, for the reception of this species. Sternberg (1940b) described yet another species, T. edmontonensis , from the Edmonton Formation of Alberta, and reviewed the classification of the Hypsilophodontidae .

Based on criteria listed by Sternberg (1940b, p. 483), premaxillary, maxillary, and dentary teeth appear to be present in the Judith River Formation. They are all approximately of the same size with one notable exception, AMNH 8538 from Clambank Hollow, which may not be a hypsilophodont. The other teeth are consistently smaller than those figured by Sternberg (1940b, p. 484, figs. 2-8). AMNH 8536 is triangular in shape with a sharply pointed apex (fig. 9E, F). The anterior and posterior ridges may be straight or slightly concave, and the presence and development of denticles is variable. Denticles may be well developed on the anterior and posterior crests, or may be restricted only to the posterior crest. The anterior edge is usually straight as a result of development of a principal wear facet on the internal side.

Judging from the figures of Sternberg (1940b, p. 484, figs. 2, 3), AMNH 8539 from Clambank Hollow is probably a premaxillary tooth of Tlhescelosaurus. The denticles are faint but appear to be developed on both the anterior and the posterior edges. A wear facet is present on the anterior half of the crown, on the internal face. The crown is higher than long and constricted at the base. No cingulum is present. The root is subcylindrical in cross section and hollow. Despite the small size and early stratigraphic occurrence of these specimens it does not seem advisable to name a new species based on them.

Figures

FIG. 9. A, B. Edmontonia lorngiceps, AMNH 8543, lateral views of an isolated tooth, x 1. C, D. Palaeoscincus costatus, AMNH 8542, lateral views of an isolated tooth, x 12. E, F. Thescelosaurus cf. T. neglectus, AMNH 8536, lateral views of an isolated tooth, x 10. G, H. Ceratopsidae, AMNH 8540, lateral views of an unworn tooth, x 12. I. Dromaeosaurus albertensis, AMNH 8516, lateral view of an isolated tooth, x 12. J, K. Paronychodon lacustris, AMNH 98523, lateral views of an isolated tooth, x 12. L, M. Troodon formosus, AMNH 8518, lateral ~~~~~~~~~~~~~~~~~~~~~~~~~~~~3. views of an isolated tooth, x 12. N. 0,?Stegoceras validus, AMNH 8530, lateral views of an isolated tooth, x 1-. Dinosaur egg shell fragments. P. AMNH 8545, external view of shell (Class B). Q. Internal view. Both x 10. R. AMNH 8546, external view of shell (Class B). S. Internal view. Both x 10. T. AMNH 8548, external view of shell (Class C). U. Internal view. Both x 10. V. AMNH 8547, external view of shell (Class B). W. In- ternal view. Both x 10. X. AMNH 8544, external view of shell (Class A), x 10.