Galeops, Broom, 1912

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

GALEOPS

Galeops was selected as the nondicynodont anomodont for comparison with the dicynodont anomodonts under study. The midshaft region of a humerus, tibia, fibula, and the distal section of a femur from specimen SAM-PK-12261 were available for thin sectioning. The cortical thickness of all the elements with preserved midshaft regions is high, as all values exceeded 34% ( Table 2). The bone tissue of all the limb bones consists of poorly vascularized (3.9% average) fibrolamellar bone interrupted by (sometimes multiple) annuli of lamellar bone ( Fig. 2A ), apart from the fibula where no annuli were observed. The small, narrow vascular canals are evenly distributed throughout the cortex and arranged in longitudinal primary osteons with radial anastomoses, but more frequently as simple canals. Secondary remodelling, including a few small secondary osteons, was observed in the perimedullary regions of most of the elements. A thick region of parallel-fibred bone containing annuli was observed in the midcortex of the tibia and is also present towards the periphery in the femur and in one region of the fibula.

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.