Positional behavior and vertebral morphology in atelines and cebines

Area of Science:

• Primate evolutionary biology
• Comparative anatomy
• Paleoanthropology

Background:

• Atelines exhibit convergent postcranial anatomy with hominoids, particularly the vertebral column.
• Existing knowledge of ateline vertebral morphology is primarily qualitative, with limited functional interpretations.
• Vertebral morphology in other platyrrhines remains largely unexplored.

Purpose of the Study:

• To investigate vertebral form and function in atelines and cebines.
• To analyze spinal loading regimes and vertebral morphometrics in relation to positional behaviors.
• To compare lumbar adaptations for resisting bending and facilitating leaping.

Main Methods:

• Direct field observations of axial postures and movements in Ateles geoffroyi, Alouatta palliata, Cebus capucinus, and Saimiri oerstedii.
• Quantitative assessment of spinal loading regimes based on observed behaviors.
• Detailed morphometric analysis of lumbar vertebrae in atelines, cebines, and Hylobates for comparative purposes.

Main Results:

• Atelines frequently adopt postures and locomotor behaviors inducing significant spinal bending loads.
• Atelines possess lumbar adaptations for resisting bending, including elongated vertebral bodies and perpendicular transverse processes.
• Saimiri exhibits features accentuating bending loads but enhancing sagittal flexibility for leaping, differing from atelines and cebines.

Conclusions:

• Lumbar vertebral morphology varies among atelines, with adaptations reflecting distinct loading patterns.
• Saimiri's lumbar morphology is specialized for leaping, contrasting with the bending-resistance adaptations in atelines.
• Convergent vertebral anatomy between atelines and hylobatids is likely driven by similar spinal loading patterns rather than shared behaviors.