Osteohistological analysis reveals unusual bone tissue patterns in Temminck's ground pangolin ( Smutsia temminckii )

Abstract

Temminck's ground pangolin is one of Africa's most threatened mammals, yet little is known about its skeletal biology. This study provides the first osteohistological analysis of its limb bones, documenting patterns of growth, remodelling and skeletal reinforcement. Limb bones exhibit extensive cortical remodelling, with substantial portions of the cortex being composed of compacted coarse cancellous bone, endosteal bone and secondary osteons, together with abundant resorption cavities. Growth marks occur in all elements, but the absence of outer circumferential lamellae and persistence of open vascular canals indicate continued growth and a lack of skeletal maturity despite the presence of up to four annual growth cycles. Extensive skeletal reinforcement occurs throughout the limbs, although elements employ distinct osteohistological patterns. Comparison with the aardvark reveals alternative pathways of skeletal reinforcement, with ground pangolins showing relatively greater secondary remodelling in the hind limb. Ground pangolins are further distinguished by abundant, incompletely infilled resorption cavities extending into the middle and outer cortex, suggesting an unusual pattern of intracortical remodelling. The exceptionally low basal metabolic rate of S. temminckii may contribute to these patterns, although this relationship remains to be tested. These findings provide new insights into the skeletal biology of this poorly studied mammal.