Dendrerpeton is not well enough known for an exact comparison with Erpetosaurus obtusus, but Cope separated the latter from Dendrerpeton on the position of the orbits and the broadly rounded muzzle. This species differs from the other species of the genus in the form of the cranium, as well as in the characters which separate it from Dendrerpeton.
| Measurements of the Type of Erpetosaurus obtusus Cope. | |
| mm. | |
| Median length of the skull | 48 |
| Width of skull at posterior border | 56 |
| Width across orbits | 37 |
| Length of orbit | 12.5 |
| Width of orbit | 7 |
| Interorbital space | 15 |
| Diameter of nostril | 1.5 |
| Diameter of pineal foramen | 1.75 |
Two other specimens, Nos. 8602 G and 8608 G of the American Museum, are associated in this species.
Erpetosaurus tabulatus Cope.
Cope, Proc. Amer. Phil. Soc., XVI, p. 577 (Tuditanus tabulatus).
Moodie, Jour. Geol., 17, p. 52, figs. 8, 9, 1909.
Moodie, Bull. Amer. Mus. Nat. Hist., XXVI, pp. 347, 351, pl. 59, fig. 2; pl. 62, fig. 2, 1909.
Type: Specimen in the Zoological Collection of Columbia University.
Horizon and locality: Linton, Ohio, Coal Measures. ([Plate 25, fig. 2.])