Extraordinary grip strength and specialized myology in the hyper-derived hand of Perodicticus potto?

Abstract

Previous behavioral reports of the African lorisid, Perodicticus potto, have speculated that these animals have an extraordinary grip strength. This ability is hypothesized to be facilitated by a range of anatomical features within the forelimb, ranging from the presence of a retia mirabilia in its wrist to the hyper-abduction of its pollex. Despite numerous behavioral reports, however, this claim of extraordinary grip strength has not been empirically substantiated. This study quantifies the physiological cross-sectional area of the digital flexor muscles within P. potto. These data are compared with a broad primate sample, including several similarly sized strepsirrhines. Contrary to expectation, we found that P. potto actually has relatively below-average digital flexor PCSA. However, we identified other myological characteristics in the upper limb of P. potto that were unexpected, including the largest brachioradialis muscle (an elbow flexor) among our primate sample, and – despite P. potto having only a vestigial second digit – an independent digital extensor indicis that is absent in almost a quarter of our primate sample.