Dental integration and modularity in pinnipeds

Area of Science:

• Evolutionary biology
• Comparative anatomy
• Paleontology

Background:

• Morphological integration and modularity are key concepts in evolutionary biology, influencing how traits evolve under selection.
• Understanding these principles in simplified dentitions, like those of pinnipeds (seals, sea lions), is crucial for evolutionary insights.

Purpose of the Study:

• To investigate dental integration and modularity in representative otariid and phocid species.
• To compare these patterns with mammals possessing complex dentitions and explore their evolutionary implications.

Main Methods:

• Analysis of dental morphology and occlusion in Eumetopias jubatus, Callorhinus ursinus (otariids), Phoca largha, and Histriophoca fasciata (phocids).
• Quantification of dental integration and modularity, relating them to occlusion and tooth-size variability.

Main Results:

• Dental integration was significantly stronger in otariids than phocids.
• Stronger integration correlated positively with dental occlusion and negatively with modularity and tooth-size variability.
• Canines and the third upper incisor formed a highly integrated module, likely functioning as occlusal guides.

Conclusions:

• Pinniped dentition exhibits strong integration, exceeding or matching that of mammals with complex dentitions.
• This integration is hypothesized to be driven by dental occlusion and facilitated by reduced modularity.
• Reduced modularity is proposed as an adaptation to aquatic life, associated with pierce-feeding and loss of mastication.