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.

DiceCT Analysis of the Extreme Gouging Adaptations Within the Masticatory Apparatus of the Aye‐Aye (Daubentonia madagascariensis)

“…Finally, the directionality of constituent fascicles contributes towards a muscle's line of action and the efficiency with which this directional force is imparted (MacIntosh et al, 2006). Consequently, quantifying muscle internal architecture and fascicle orientation is critical to our understanding of musculoskeletal adaptation and specialization, and extensive research into inter-specific trends in architectural properties has been conducted across a wide range of vertebrate taxa (e.g., Sacks and Roy, 1982;Anapol and Barry, 1996;Payne et al, 2006;Oishi et al, 2008;Michilsens et al, 2009;Hartstone-Rose et al, 2012;Mathewson et al, 2014;Ogihara et al, 2017;Curtis and Santana, 2018;Hartstone-Rose et al, 2018;Boettcher et al, 2019).…”

A primate with a Panda's thumb: The anatomy of the pseudothumb of Daubentonia madagascariensis

“…madagascariensis. In addition to these two lemurid comparative specimens, we have dissected several other primate taxa (e.g., see Leischner et al 2018, Boettcher et al 2019, and have never seen another primate taxon with a cartilaginous prepollex or this muscle configuration. Consequently, no evidence for the presence of this digital adaptation can be observed within comparative taxa.…”

The Forearm Musculature of the Gray Mouse Lemur (Microcebus murinus): An Ontogenetic Study

“…Muscle mass and fascicle length data were combined to calculate the PCSA of each muscle, using the following formula modified from Schumacher (): in which a constant of 1.0564 g/cm 3 was used to represent muscle density (following Murphy and Beardsley, ). As recent publications on the forearm musculature of primates have demonstrated the negligible impact of pennation angle on muscle force (van Leeuwen et al ., ; Boettcher et al ., ), a conversion into RPCSA (as per Anapol and Barry, ) was not used.…”

“…Several attempts have recently been made to characterize variation in forearm muscular anatomy across the primate order (Gibbs et al ., ; Aversi‐Ferreira et al ., ; Diogo and Wood, ; Lemelin and Diogo, ; Leischner et al ., ; Boettcher et al ., ). Interestingly, while no consistent phylogenetic trends are reported to describe such variation, locomotor repertoire appears closely correlated with forearm functional capacity.…”