Kannemeyeria

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 : 356

KANNEMEYERIA

Several elements were examined for this genus ( Table 1). However, bone histology of an ulna and femur (NMQR2674a, b) are the most informative as many of the other Kannemeyeria elements are diagenetically altered. The bone tissue exhibits moderately vascularized fibrolamellar bone with the vascular canals arranged as longitudinally orientated primary osteons with short anastomoses. Annuli and LAGs, which are sometimes multiple, interrupt the primary bone at intervals. A free medullary cavity is absent and is completely filled by trabecular bone. Secondary remodelling, with numerous secondary osteons (larger than those observed in the other genera), is extensive and reaches near the periphery in places. Compact coarse cancellous bone is also observed in the perimedullary region. Although less extensive compared to the other genera exhibiting this feature, enlarged channels arranged in a few circumferential rows are present in the mid and outer cortex of femur NMQR2674b ( Fig. 4F ).

NMQR789 is a midshaft fragment of an unidentified Kannemeyeria limb bone. It is extensively remodelled and only a thin layer of primary compact bone is present at the periphery. A free medullary cavity is absent and numerous, prominent secondary osteons extend to at least midway into the cortex. The thin layer of primary bone consists of poorly vascularized fibrolamellar bone with prominent, sometimes multiple LAGs at the periphery. Sharpey’s fibres are present in a localized region of the bone.

NMQR3631 is a rib and consists of fibrolamellar bone interrupted by a midcortical LAG and multiple LAGs at the periphery. Secondary remodelling is prominent and extends into the midcortex. The outer cortex contains primary bone tissue with vascular canals arranged in a subreticular network. A free medullary cavity is absent and Sharpey’s fibres are observed in one region of the bone.

Figures

Figure 4. Permo-Triassic dicynodont bone histology. A, juvenile Dicynodon humerus SAM-PK-K5576d; B, subadult Dicynodon humerus NMQR3633a; C, subadult Lystrosaurus maccaigi ulna NMQR3663b; D, juvenile Lystrosaurus declivis tibia NMQR735b; D, E, adult Lystrosaurus humerus (possibly Lystrosaurus declivis) NMQR3678; F, late subadult Kannemeyeria femur NMQR2674b. Arrows indicate enlarged channels in all genera. Scale bars: D, E = 500 mm; A, B, C, F = 413 mm.