Cistecephalus

Botha-Brink, Jennifer & Angielczyk, Kenneth D., 2010, Do extraordinarily high growth rates in Permo-Triassic dicynodonts (Therapsida, Anomodontia) explain their success before and after the end-Permian extinction?, Zoological Journal of the Linnean Society 160 (2), pp. 341-365 : 351

CISTECEPHALUS

The bone tissue of Cistecephalus was examined using an ulna and radius from a single individual (NMQR1465). Both elements have relatively thin bone walls with a cortical thickness of 27% for the ulna and 25% for the radius ( Table 2). The elements exhibit moderately vascularized fibrolamellar bone interrupted by at least three annuli. The annuli are more prominent in the radius. A thick layer of circumferential endosteal lamellar bone surrounds the medullary cavities in both elements. The vascular canals consist of longitudinal primary osteons with short radial anastomoses. Poorly vascularized, parallel-fibred bone is observed in one small region of the radius, but is prominent in a thick layer around the whole of the bone periphery in the ulna ( Fig. 3A ). A thick layer of endosteal bone also surrounds the medullary cavity of the latter element.

Figures

Figure 3. Permo-Triassic dicynodont bone histology. A, subadult Cistecephalus ulna NMQR1465b; B, early subadult Dicynodontoides tibia NMQR479a; C, adult Rhachiocephalus ulna SAM-PK-3714a; D, subadult Tropidostoma tibia SAM-PK-K9960c; E, adult Oudenodon femur SAM-PK-K4807a; F, adult Aulacephalodon femur NMQR3016. Arrows indicate enlarged midcortical channels in Rhachiocephalus and Aulacephalodon. Scale bars: A, D, E = 500 mm; B, C, F = 413 mm.