Paronychodon lacustris Cope, 1876a

Figures 8S, T; 9J, K

Paronychodon lacustris COPE, 1876a, p. 256.

Zapsalis abradens COPE, 1876b, p. 345.

Tripriodon caperatus MARSH, 1889b, pl. 3, figs.18-22.

The genus was originally described by Cope (1876a, p. 256) from detached teeth obtained from the Judith River Formation. Zapsalis abradens was also described by Cope (1876b, p. 345) from the same area and is a larger, worn tooth of Paronychodon. Teeth referable to Paronychodon lacustris were named Tripriodon caperatus (Marsh, 1889b, pl. 3, figs. 18- 22) because of a supposed identity as the incisors of the multituberculate Meniscoessus Cope (= Dipriodon Marsh). Clemens (1963b, pp. 85-86) showed that Meniscoessus incisors were significantly different from Paronychodon and Estes (1964) has demonstrated that P. lacustris is a carnivorous dinosaur.

The rare genus Paronychodon is represented in the collection by about six teeth of various sizes. The largest (AMNH 8522, fig. 8S, T) has a length of 13 mm. and a basal width of about one-third the length, and the smallest (AMNH 8523, fig. 9J, K) has a height of 4.8 mm. and a basal width of about 2.8 mm. Other differences in morphology also exist. AMNH 8522, from Clambank Hollow, is relatively less curved than teeth of Deinodon. At least four ridges were present on the internal side of the crown but these have been worn down. The smaller teeth are more curved and are not denticulated on the posterior or anterior side, although sharp ridges are present.