Fig. 29. Skeleton of Cephalerpeton ventriarmatum Moodie. × 1.
pf, prefrontal; cl, clavicle; m, mandible; h, humerus; j, jugal; mx, maxilla; or, orbit; ph, phalanges of hand; par; parietal; po, postorbital; r, radius; sp, sclerotic plates; u, ulna; vs, ventral scutellæ.
Portions of 4 sclerotic plates are preserved in the right orbit. These measure 0.5 by 0.75 mm. The orbits are large and the interorbital space is less than the transverse diameter of the orbit. Thirteen teeth, apparently pleurodont, are preserved on the left maxilla. They are short, sharply pointed, smooth, and unequal. The first 2 left maxillary teeth from the anterior end are short; then follows a tooth which is one-third longer than these two; the fourth tooth is somewhat shorter than the third; the fifth and sixth are still shorter and are practically equal in size, though somewhat larger than the first two.
The right mandible is preserved almost entire, though so badly eroded that little can be said of its structure. Impressions of 12 teeth are present on the mandible and all are, apparently, equal. The cotylus seems to have been far posterior and an angle of the mandible projected slightly back of the skull.
There remain only a few indefinite impressions of the cervical vertebræ. The union of the skull with the vertebral column is obscured and lost. Impressions of the dorsal vertebræ are well preserved, and wax molds made from these show the structure of the dorsal vertebræ surprisingly well. They are long and cylindrical, with the median portions slightly constricted by a deep pit on each side of the low neural ridge, which takes the form observed in Thyrsidium, Molgophis, Phlegethontia, Dolichosoma ([fig. 8]) and other genera. The vertebræ are strongly amphicœlous and the notochord was probably persistent. The sides of the vertebræ are smooth.
The ribs are all intercentral in position; the anterior ones very broad near the base, recalling the broadly expanded ribs described by Schwarz ([540]) for Scincosaurus, Ptyonius, Thyrsidium, and other genera. Posteriorly the ribs become slender and cylindrical. They are all rather long and distinctly curved, with probably a cartilaginous tip.
There is preserved a single element of the right side of the pectoral girdle. This is, I think, the coracoid, an element which has hitherto escaped observation among the American Microsauria. It is long and spatulate at both ends, with the median portion apparently almost cylindrical, not unlike that described by Credner ([181]) for the coracoid of Branchiosaurus, save that the lower end of the branchiosaurian coracoid is acuminate. In the present form it is spatulate. Its relations with the other elements of the pectoral girdle have never been satisfactorily determined.
The fore limbs are both partially preserved. The humerus of the right side is complete. It is greatly elongated for a microsaurian. The form of the element is not unlike that of a lizard, with the lower end of the bone spatulate and endochondrium well developed. Very little difference can be seen between the form of the arm bones, which represent the radius and ulna. They are both elongated, with constricted median portion and expanded truncate ends. The carpus is unossified and the cartilage has left no trace of the elements.
The right hand has two metacarpals preserved, which are fully half as long as the radius and ulna. They are separated some little distance from the ends of these elements, though this may be due to post-mortem shifting. The carpus may, however, have been broad. On the left side are preserved portions of the humerus, radius, ulna, and 3 metacarpals, lying close to the vertebral column. The carpal space is not so large on the left as on the right. The ventral armature is well preserved in a narrow patch about an inch in length. The chevron-shaped rods are quite large, there being 2 of them in 1 mm.
| Measurements. | |
| mm. | |
| Entire length of fossil | 98 |
| Length of skull | 22 |
| Width across base of skull | 28 |
| Long diameter of eye | 10.5 |
| Transverse diameter of eye | 8 |
| Interorbital space | 4 |
| Length of mandible | 26 |
| Depth of mandible at coronoidal region | 3.5 |
| Depth of dentary | 2 |
| Length of long tooth | 2 |
| Diameter of long tooth at base | .5 |
| Length of preserved portion of vertebral column | 64 |
| Length of a centrum | 3 |
| Median width of a centrum | 1.5 |
| Length of rib | 6.5 |
| Width of rib at base | .33 |
| Length of coracoid | 5 |
| Width of coracoid at anterior end | 2.5 |
| Length of carpal space | 5 |
| Length of humerus | 18 |
| Width of shaft | 1 |
| Distal width of humerus | 4 |
| Length of radius and ulna | 10.5 |
| Length of metacarpal | 6 |
| Length of ventral armature preserved | 24 |
| Number of rods in length of 5 mm | 10 |