Patterns and magnitudes of craniofacial covariation in extant cercopithecids

Area of Science:

• Primate Paleontology
• Comparative Anatomy
• Evolutionary Biology

Background:

• The primate cranium houses sensory organs and is crucial for vertebrate evolution.
• Previous research highlights cranial integration and modularity, but often overlooks sensory structures like orbits.
• Understanding craniofacial covariation, especially around the orbits, is key to primate evolutionary studies.

Purpose of the Study:

• To investigate patterns and magnitudes of craniofacial covariation in extant cercopithecids.
• To specifically examine the covariation related to the orbits within the primate skull.
• To assess how these patterns differ across cercopithecid subfamilies, tribes, and genera.

Main Methods:

• Quantitative analysis using 38 homologous cranial landmarks.
• Data collected from 291 individuals across 11 genera of cercopithecid monkeys (Cercopithecidae).
• Statistical examination of craniofacial covariation patterns and magnitudes.

Main Results:

• Craniofacial covariation patterns and magnitudes vary significantly across Cercopithecidae at multiple taxonomic levels.
• Papionins, particularly the genus Papio, exhibit the strongest craniofacial integration.
• Colobines, especially Presbytis, show significantly weaker covariation; orbital height is highly constrained and covaries less with other cranial measurements.

Conclusions:

• Craniofacial covariation and modularity patterns are not uniform across all primates, cautioning against broad generalizations.
• Orbital constraints have significant implications for understanding the evolution of primate vision and cranial diversity.
• These findings are vital for accurate interpretation of fossil primate taxonomy, as craniofacial covariation influences key differentiating phenotypes.