Palmaris Longus in the Anubis Baboon (Papio anubis): A Conservative Single-Tendon Pattern with Rare Distal Bifurcation

The palmaris longus (PL) remains insufficiently quantified in cercopithecoids (Cercopithecoidea), despite growing comparative data across primates. We examined adult archival material of the Anubis baboon (Papio anubis) to document PL presence, tendon configuration and topography, describe muscle–tendon morphometrics, and test for side-, sex- and size-related effects. A PL was present in all limbs. Two tendon configurations were observed: a single tendon inserting into the palmar aponeurosis (Type I, 87.0%) and a bifurcated tendon with both medial and lateral slips inserting into the palmar aponeurosis (Type II, 13.0%). No side- or sex-related differences were found in variant distribution. Males showed larger absolute values for selected measurements, but these differences were not independent of antebrachial size. PL lengths and interstyloid distances were strongly correlated with antebrachial size, indicating overall scaling with limb dimensions. These findings identify a species-level pattern in which PL is consistently present and predominantly unbranched, with only occasional distal bifurcation. The data establish a comparative anatomical baseline for Papio and broaden the available evidence on PL morphology in non-human primates.