Fig. 16. Right mandible—½ natural size.
The two halves of the lower jaw are completely fused at the symphysis. The horizontal ramus is thick, but low dorso-ventrally, giving the appearance of a slender jaw. The posterior angle is prolonged backward and bent inward. The fossa for the masseter muscle, while large, is but faintly outlined. The ascending ramus hardly rises above the level of the teeth, except as the slender coronoid projects to a good height above the articular condyle and curves backward over it.
| Measurements | ||
|---|---|---|
| Lower dentition, | total length | 114 mm. |
| incisors, length | 20 mm. | |
| canine, length | 8 mm. | |
| premolar 2 to 4 | 35 mm. | |
| molar 1 to 3 | 42 mm. | |
| Mandible, | total length | 188 mm. |
| height under molar 1 | 24 mm. | |
| height to top of coronoid | 95 mm. | |
The dorsal vertebrae have short, wide, and somewhat depressed centra (in this individual the epiphyses are free, though this is the only indication of youth). The lower rib facets are small, that on the posterior margin of the centrum being a mere streak, while the one on the anterior margin is narrow. The upper rib facet is a rounded convex surface on the end of a short stout transverse process. The prezygapophyses are convex surfaces, wide transversely, but narrow in the antero-posterior direction, while the postzygapophyses are correspondingly narrow concave facets under the rear of the spines. The spines are thin and high, and the neural canal is nearly circular in section.
The lumbar vertebrae have laterally compressed, deep centra, with very long transverse processes, shorting spines, and zygapophyses of the subcylindrical interlocking type. In all their features the vertebrae resemble those of Theosodon, being nearly as highly specialized and in the same manner.
| Measurements of Typical Vertebrae | |||
|---|---|---|---|
| Dorsal vertebra | No. 7, | length | 23 mm. |
| width of centrum | 22 mm. | ||
| Dorsal vertebra | No. 9, | length | 28 mm. |
| Lumbar vertebra | No. 2, | length | 29 mm. |
| Lumbar vertebra | No. 2, | width of centrum | 24 mm. |
| Lumbar vertebra | No. 2, | width across transverse processes | 160 mm. |
The femur is short and very stocky. The rounded head is carried on a short neck, and does not rise nearly as high as the greater trochanter, the sulcus for the round ligament being a broad, deep notch on the posterior margin. The greater trochanter is rugose, heavy, and high, but not incurved at the top. The lesser trochanter is a small, thin ridge well below the head. The third trochanter is a large, thin process, projecting almost directly backward, though curved inward at the end, and is situated well below the middle of the bone. The shaft of the femur is flattened above, but thick, and changes in the lower part to subcylindrical. The condyles are small, subequal in size, and widely separated, while the rotular trochlea is relatively wide and shallow.
Fig. 17. Left femur anterior side—½ natural size.
