The vertebral column is represented by a ridge showing along the median plane of the specimen. Its characters can not be ascertained. There are a few evidences of ribs. They represent long, slender, non-alate elements, their mode of articulation with the vertebræ being obscured by the plate-like ventral armature which covered the abdomen of the animal.
The pectoral girdle is represented by the remains of three elements which are interpreted as being the interclavicle and the two clavicles. The interclavicle is broad and is rounded posteriorly. There is no evidence of the usual acumination posteriorly. The element is nearly as wide as long. There is a prominent longit udinal keel on the ventral surface of the interclavicle and radiating lines which may indicate the courses of blood-vessels or nerves or may be the ornamentations of the element, probably the latter. The clavicle has the usual microsaurian form. It has three points and is truncate exteriorly. It is ornamented with radiating grooves of a shallow and not strongly pronounced character. There is no evidence of the coarse sculpture of the later forms. If the scapula is represented it is merely by an indeterminate fragment insufficient for description.
The pectoral limbs are preserved nearly entire. The left fore limb lacks only a few phalangeal bones, and these were preserved with the remainder of the skeleton but were lost in the mining process. The humerus is an extraordinary element on account of its robust dimensions. It is very stoutly built and represents a powerful limb. It is expanded at each extremity and the width of its shaft is about equal to one-fourth of its length. The ulna and radius present the same characters as the humerus, i.e., in being robust, with stout shaft and expanded ends. The ulna is slightly longer than the radius and has an expanded upper end. The radius is short and does not have the proximal expansion. The carpus was cartilaginous. Its position is represented by a blank space on the coal. There are 4 digits preserved and in all probability this was the entire number. The metacarpals are elongate and expanded at the extremities. The first and second digits are represented nearly complete. The first digit is extremely interesting in the possession of a claw-like terminal phalanx which much resembles that of some lizards. There are 3 phalanges in the first digit and 4 in the second. The phalangeal formula may have been 3-4-4?.
The ventral scutellation of this species is of an unusual character. It consists of broad, imbricated scutes which are in a single piece and which are arranged in the usual chevron pattern. The scutes were, apparently, broadest in the middle and tapered somewhat at the extremities. This character alone is sufficient for separating the genus from that of any other known form.
The genus finds its nearest allies in the forms of the species of the genus Sauropleura, in which Cope formerly located the present species. The skull of the form described as Tuditanus radiatus Cope is quite similar to the present form, both in the sculpturing and arrangement of the elements. The characters wherein the present form resembles the species of Sauropleura are the possession of broad pectoral plates and strong, digitate limbs. The general form of the body and skull is different in the two groups. It is slender in Sauropleura and decidedly stout, short, and heavy in Saurerpeton.
| Measurements of the Type. | |
| mm. | |
| Length of specimen | 130 |
| Median length of skull | 51 |
| Width of skull at posterior border | 62 |
| Width of skull across orbits | 48 |
| Length of orbit | 14 |
| Width of orbit | 10 |
| Interorbital space | 16 |
| Length of longest tooth preserve | 14 |
| Length of shortest tooth preserved | 1 |
| Length of the interclavicle | 26 |
| Width of interclavicle, maximum | 23 |
| Length of clavicle | 22 |
| Width of clavicle | 18 |
| Length of abdominal scutes | 28 |
| Length of humerus | 19 |
| Width of humerus at upper end | 6.5 |
| Length of ulna | 11 |
| Length of radius | 9 |
| Length of metacarpal | 3 |
| Length of first digit | 12 |
| Length of terminal phalanx | 3.5 |
| Length of lower jaw on the curve | 70 |
| Width of lower jaw, maximum | 8 |
| Length of rib | 30 |
Cope, Proc. Am. Phil. Soc., XXXVI, p. 83, pl. iii, fig. 1, 1897.
Type: Ctenerpeton alveolatum Cope.