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Abstract ObjectivesDespite the longstanding importance of grasping adaptations in theories of primate evolution, quantitative data on primate grasping strength remain rare. We present the results of two studies testing the prediction that callitrichines—given their comparative retreat from a small‐branch environment and specialization for movement and foraging on tree trunks and large boughs—should be characterized by weaker grasping forces and underdeveloped digital flexor muscles relative to other platyrrhines. MethodsFirst, we directly measured manual grasping strength in marmosets (Callithrix jacchus) and squirrel monkeys (Saimiri boliviensis), using a custom‐constructed force transducer. Second, we reanalyzed existing datasets on the fiber architecture of forearm and leg muscles in 12 platyrrhine species, quantifying digital flexor muscle physiological cross‐sectional area (i.e., PCSA, a morphometric proxy of muscle strength) relative to the summed PCSA across all forearm or leg muscles. ResultsCallithrixwas characterized by lower mean and maximum grasping forces thanSaimiri, and callitrichines as a clade were found to have relatively underdeveloped manual digital flexor muscle PCSA. However, relative pedal digital flexor PCSA did not significantly differ between callitrichines and other platyrrhines. ConclusionsWe found partial support for the hypothesis that variation in predominant substrate usage explains variation in empirical measurements of and morphological correlates of grasping strength in platyrrhines. Future research should extend the work presented here by (1) collecting morphological and empirical metrics of grasping strength in additional primate taxa and (2) extending performance testing to include empirical measures of primate pedal grasping forces as well.
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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 withinP. potto. These data are compared with a broad primate sample, including several similarly sized strepsirrhines. Contrary to expectation, we found thatP. pottoactually has relativelybelow‐average digital flexorPCSA. However, we identified other myological characteristics in the upper limb ofP. pottothat were unexpected, including the largest brachioradialis muscle (an elbow flexor) among our primate sample, and – despiteP. pottohaving only a vestigial second digit – an independent digital extensor indicis that is absent in almost a quarter of our primate sample.
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- PAR ID:
- 10671944
- Publisher / Repository:
- Anatomical Society
- Date Published:
- Journal Name:
- Journal of Anatomy
- Volume:
- 235
- Issue:
- 5
- ISSN:
- 0021-8782
- Page Range / eLocation ID:
- 931 to 939
- Subject(s) / Keyword(s):
- grip strength myology Perodicticus potto arboreality forearm functional morphology muscle architecture PCSA
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/joa.13051
