Locomotor behavior and skeletal morphology of two sympatric pitheciine monkeys, <i>Pithecia pithecia</i> and <i>Chiropotes satanas</i>

TLDR

Observations align with known primate and mammalian locomotor patterns and biomechanical predictions. The study compared postcranial skeletons and limb proportions to link morphology with locomotor behavior. Pithecia pithecia primarily leaps, Chiropotes satanas mainly walks on all fours, and skeletal similarities in Cacajao calvus and fossil Cebupithecia sarmientoi support these locomotor patterns.

Abstract

Field observations of two sympatric pitheciine species reveal that the positional repertoire of the white-faced saki, Pithecia pithecia, is dominated by leaping behaviors, whereas the bearded saki, Chiropotes satanas, is predominantly quadrupedal. Examination and comparison of the postcranial skeletal morphologies and limb proportions of these species display numerous features associated with their respective locomotor behaviors. These observations accord with associations found in other primate and mammalian groups and with predictions based on theoretical and experimental biomechanics. Preliminary observations of the skeletal morphology of Cacajao calvus demonstrate a marked similarity to that of Chiropotes. The fossil platyrrhine Cebupithecia sarmientoi displays greater similarity to Pithecia, suggesting that its positional repertoire also included significant leaping and clinging behaviors.