The specimen on which the species is based is composed of the greater portion of a small skull preserved in the hard shale from Cannelton, Pennsylvania, and was collected by Mr. R. D. Lacoe, of Pittston, Pennsylvania. The characters of the specimen had not previously been determined, since the museum label and number had partially obscured the snout of the skull. The skull is very small, but has the form assumed by other members of the genus. The specimen may belong to a young individual, but even though it does, it is, nevertheless, quite distinct from the other species of Erpetosaurus. At first sight the specimen looks like a broken scute of some larger form. Close inspection, however, revealed the two impressions representing the orbits, and a Zeiss binocular revealed the characters. The large size and anterior position of the orbits, the character of the sculpturing, the presence of the posterior table of the skull, as in Erpetosaurus (Tuditanus) tabulatus Cope, are the characters on which a specific diagnosis is possible. The specific characters which distinguish this form from E. tabulatus Cope, its nearest ally, are the slight development of the posterior table, the more delicate form of the sculpturing, the more posterior position of the orbits, and the varying shape assumed by the parietals in the two species. Any one of these characters would be valid as a specific character.
The pineal eye is indistinct, but is observed to lie in the broken tract in the median line of the skull, in the middle of the portion posterior to the orbits. The interorbital space is equal to the width of the orbit. The orbits themselves are slightly oval and not round, as in the case of E. tabulatus Cope.
The skull elements are sculptured with radiating grooves and ridges, and on the postparietals and tabulare the grooves take the form of pits in a row, which undoubtedly represent the occipital cross-commissure of the lateral-line system first observed in a microsaurian by Andrews ([8]) in the skull of Ceraterpeton galvani Huxley. The supraorbital canal is represented by a slight elongate depression observable over each orbit and extending, in one case, for about 5 mm. The presence of the circular arrangement of the lateral-line canals in the jugal region is suggested by a depression on the posterior edge of the squamosal.
The portion of the skull anterior to the orbits is wanting, curiously enough, just as in Erpetosaurus tabulatus Cope. In the remainder of the skull, the post-parietals, the tabulare, the parietals, the supratemporal, and a portion of the right frontal can be detected, although the boundaries of but three can be accurately defined. The depression bounding the anterior outline of the skull is taken to be the impress of the mandible, in which case this structure would be of some depth, as in the case of the mandible associated with E. tabulatus Cope, described below.
This specimen is of interest in respect to the presence of the lateral-line canals, its small size, and its generic identity with forms from Ohio. There is still another form known from the Cannelton slates, described below as Erpetosaurus (Tuditanus) sculptilis Moodie.
| Measurements of the Type of Erpetosaurus minutus Moodie. | |
| mm. | |
| Length of skull | 18 |
| Posterior width of skull | 17 |
| Width of skull across orbits | 14 |
| Length of orbit | 4.5 |
| Width of orbit | 3.5 |
| Interorbital width | 3.5 |
Erpetosaurus sculptilis Moodie.
Moodie, Jour. Geol., 17, No. 1, p. 61, figs. 11, 12, 1909 (Tuditanus sculptilis).
Moodie, Bull. Am. Mus. Nat. Hist., XXVI, p. 347, 1909 (Erpetosaurus sculptilis).