. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. Right femur, In ventral and dorsa! views; at right, proximal and distal viev/s {dorsal aspect above). X /3- the curvature of the shaft characteristic of sphenacodonts is absent. Particularly char- acteristic is the ventral trochanteric system. There is a well-developed internal tro- chanter from which, in contrast to sphena- codonts and ophiacodonts, a ridge descends the under side of the shaft diagonally to- ward the external condyle. There is little indication of a distinct fourth trochanter along this ridge, a
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. Right femur, In ventral and dorsa! views; at right, proximal and distal viev/s {dorsal aspect above). X /3- the curvature of the shaft characteristic of sphenacodonts is absent. Particularly char- acteristic is the ventral trochanteric system. There is a well-developed internal tro- chanter from which, in contrast to sphena- codonts and ophiacodonts, a ridge descends the under side of the shaft diagonally to- ward the external condyle. There is little indication of a distinct fourth trochanter along this ridge, and likewise little develop- ment of the posterior proximal branch of the Y-shaped ridge system, the intertro- chanteric fossa thus being shallow posteri- orly. In sphenacodonts, and to a lesser degree in some ophiacodonts, the proximal articular surface extends along the proximal portion of the posterior margin of the shaft; here, as in other edaphosaurs, this surface is confined to the proximal end of the bone. Proximally, on the dorsal surface of the shaft, there is sometimes seen, toward the posterior margin, a rugose area for muscle attachment. Unique is the presence at the anterior margin of a very distinct rugose ridge, about 25 mm long, likewise presum- ably for muscle attachment; this is clearly seen in two specimens. The external condyle, as in other edaphosauroids, projects very markedly beyond the internal (medial) one, and in a well developed specimen the tip of this condyle markedly overhangs the articular surface for the tibia below it, as it does in other edaphosaiuoid femora in which ossification is well advanced. Tibia (Fig. 12). The tibia is, as noted earlier, relatively short, with a length only three-fifths or less that of the femur. As with other limb bones, the tibia is very broad, notably its head. The width of the head in one specimen is about 57 per cent. Please note that these images are extracted from scanned page images that may have been digitally e
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Keywords: ., bookauthorharvarduniversity, bookcentury1900, booksubjectzoology
