Diictodon (Ray & Chinsamy, 2004)

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 : 349

DIICTODON

The bone tissue of a femur, radius, and ulna from a single individual (NMQR400) was analysed in this study. However, Ray & Chinsamy (2004) recently completed a comprehensive bone histology study of this genus; therefore, a detailed description will not be presented here. The results in this study agree with those of Ray & Chinsamy (2004). The cortical thickness of Diictodon is high (between 20 and 41%, increasing over ontogeny, Ray & Chinsamy, 2004) and the bone tissue consists of poor to moderately vascularized (8% average for subadults; 5.8% for adults) fibrolamellar bone interrupted by faint, narrow annuli, notably similar to that of Dicynodontoides . The bone tissue becomes poorly vascularized, parallel-fibred bone towards the periphery in adults ( Ray & Chinsamy, 2004). The vascular canals are arranged either as longitudinally orientated primary osteons or in a subreticular pattern. Enlarged channels, such as those seen in Eodicynodon , are absent ( Fig. 2D ).

Figures

Figure 2. Permian dicynodont bone histology. A, adult Galeops humerus SAM-PK-12261a; B, early subadult Eodicynodon femur NMQR2996a; C, late subadult Eodicynodon femur NMQR3153a; D, late subadult Diictodon SAM-PK-K7725; E, subadult Endothiodon tibia SAM-PK-5605c; F, adult Endothiodon humerus SAM-PK-K6618a. Arrows indicate enlarged midcortical channels. Enlarged channels are absent in Galeops, Diictodon, and Endothiodon. However, subadult Endothiodon reveals rapid, sustained growth with an average channel area of 13%. Scale bars: B, C = 500 mm; A, D, E, F = 413 mm.