The mesopodial elements, unlike what is described for Cephalerpeton, are quite dissimilar in form, recalling the condition in Mesosaurus brasiliensis McGregor. The larger element is, apparently, the ulna. It has the lower end greatly expanded and the shaft is curved outward, resembling very much a reptilian ulna. The radius is much smaller than the ulna, lacks the lower expansion, and is shorter by 1 mm.
The carpus is represented merely by a blank space, with evidences of impressions of cartilage in the sandstone. The hand of the right side contains 4 phalanges. There are 2 phalanges preserved in the first digit, including a sharp-pointed terminal phalanx, and the second digit has only the metacarpal. The third has the metacarpal and the first phalanx, which does not differ in form, but only in size, from the metacarpal. The fourth digit contains only the metacarpal. Of the left hand there are portions of 3 digits preserved, including 3 metacarpals and a phalanx, which in structure are not different from those of the right hand.
The ilium of the left side is preserved, apparently entire. It is elongate and cylindrical, its upper end adjoining the twenty-eighth vertebra. The head of the femur lies close to the lower end of the ilium, so that that element must have been suspended in the flesh, much as in modern salamanders. It could not have been of much use as a support for the body. The form of the femur is not unlike that described for the humerus, save that its lower end is smaller than the upper, while in the humerus the extremities are of equal diameter. A portion of the right femur is preserved, extending in an opposite direction to the left.
| Measurements of the Type. | |
| mm. | |
| Length of entire specimen | 64 |
| Length of portion of skull preserved | 6.5 |
| Posterior width of same | 7 |
| Width across orbits | 11 |
| Long diameter of orbit | 3 |
| Transverse diameter of orbit | 1.75 |
| Interorbital width | 4.75 |
| Length of dorsal vertebræ | 48 |
| Length of caudal series | 11 |
| Length of anterior dorsal centrum | 2 |
| Length of anterior dorsal rib | 4 |
| Length of anterior caudal rib | 1.75 |
| Length of scapula | 5 |
| Greatest width of scapula | 4.25 |
| Probable length of interclavicle | 6 |
| Width of same | 3 |
| Length of clavicle | 4.5 |
| Width of same | 1.5 |
| Length of right humerus | 6 |
| Distal width of same | 2 |
| Length of ulna | 3.25 |
| Distal width of same | 1 |
| Length of radius | 3 |
| Width of carpal space | 2 |
| Length of metacarpal | 1.74 |
| Length of first phalanx | 1.75 |
| Length of distal phalanx of right hand | .35 |
| Number of chevron rods in 1 mm. | 4 |
| Length of ilium | 2.25 |
| Length of femur | 4 |
| Proximal width of femur | 1.50 |
Mazonerpeton costatum Moodie.
Moodie, Kans. Univ. Sci. Bull., VI, No. 2, p. 341, pl. 2, fig. 3; pl. 8, fig. 4; pl. 9, fig. 2; pl. 10. 1912.
The remains on which the present species is based are inclosed in a much fractured nodule. The parts of the animal which have been identified are: a part of the skull and left mandible, two clavicles, a humerus, impressions of several vertebræ, a portion of the dorsal region of the body with several ribs, two portions of the caudal region with several ribs and unidentified fragments. ([Plate 4, fig. 3.])
The animal, from the shape and form of the ribs, is undoubtedly a branchiosaurian, since short, heavy, straight ribs have not yet been found to be associated with other than branchiosaurian structures. It is placed in the genus Mazonerpeton on account of the structure of the pectoral elements, the form of the humerus, and the length of the tail, all of which agree in structure with Mazonerpeton longicaudatum. The animal attained, perhaps, a length of 4.5 inches, while that of M. longicaudatum was about 3 inches. The tail in the present species is very long and slender, more elongate than in any other known branchiosaurian.