Plantaris tendon morphology in Papio anubis: a comparative anatomical study

The plantaris muscle shows marked variability in humans, yet comparable data from non-human primates remain limited. This study examined plantaris tendon morphology in 46 lower limbs from 23 adult Anubis baboons (Papio anubis) using standardized dissection, morphometry and a human-derived insertional classification. A plantaris muscle was present in all specimens, and tendon morphology was limited to two recurrent patterns: a narrower band-like configuration corresponding to human Type II and a broader sheet-like configuration corresponding to human Type V. Type II predominated (73.9%), whereas Type V occurred in 26.1% of limbs. Between-type differences involved tendon width, thickness and the level of the extension point relative to the calcaneus, while overall limb dimensions did not differ significantly. These findings indicate that, within the examined sample, plantaris tendon morphology in Papio anubis was restricted to two recurrent configurations rather than displaying the broader insertional spectrum reported in humans. The results provide a preliminary comparative anatomical baseline for future studies of plantaris tendon variation across primates, while broader taxonomic, geographic and population-level sampling is required before broader evolutionary or species-wide interpretations can be drawn.