Family AMPHIBAMIDÆ new family.
Small, lizard-like, terrestrial or semi-aquatic, megacephalic microsaurians, known from 3 species. The family characters are the huge size of the head as compared to the body, the short, stumpy body with about 25 short dorsal vertebræ, a very short tail, phalanges clawed, pubis of calcified cartilage, sclerotic plates in the orbit to the number of 29 or 30 in each, ventral armature well developed. Teeth anisodont, sharp, conical, non-striate.
Two genera are associated in this family: Amphibamus grandiceps Cope, known from three nearly complete skeletons; A. thoracatus Moodie, known from a single incomplete skeleton; Cephalerpeton ventriarmatum Moodie, anterior portion of body and skull. The species are all from the Mazon Creek shales and the family seems unrepresented elsewhere. It may be necessary to compare the Amphibamidæ with the Hylonomidæ when the latter group is better known, but in the light of our present knowledge the two families are distinct.
The genera may be distinguished as follows:
I. Size small, less than 3 inches in total length, skull with deeply incised tympanic notches (ear-slits) Amphibamus
II. Size relatively large, body-length 6 inches or more, teeth distinctly anisodont, skull with nearly even posterior table, limbs very long, ventral armature highly developed Cephalerpeton
Cope, Proc. Phila. Acad. Nat. Sci., 1865, pp. 134-137. Geol. Surv. Ills., 11, pp. 135-141, pl. xxxii, 1 text-fig.
Hay, Proc. Am. Phil. Soc., XXXIX, p. 120, 1900.
Moodie, Jour. Geol., XVII, p. 81, fig. 24, 1909.