Mandible strength and geometry in relation to bite force: a study in three caviomorph rodents

Area of Science:

• Paleontology
• Biomechanics
• Rodent evolution

Background:

• Caviomorpha is a diverse rodent group with varied locomotion, ecology, and diet.
• Cranio-mandibular morphology in caviomorphs is linked to dietary toughness and behaviors like digging.
• Significant differences exist in the ecology, behavior, and bite force of Chinchilla lanigera, Octodon degus, and Ctenomys talarum.

Purpose of the Study:

• To assess the structural strength of the mandible in three distinct caviomorph species.
• To relate finite element (FE) model predictions of stress to in vivo bite forces and mandibular geometry.
• To understand the functional morphology of caviomorph mandibles in relation to their ecological niches.

Main Methods:

• Utilized finite element (FE) models to simulate stresses on mandibles during incisor biting.
• Collected in vivo bite force data for comparative analysis.
• Examined interspecific variations in mandibular geometries.

Main Results:

• Ctenomys talarum exhibits a mandible best suited for strong incisor bites, evidenced by its powerful musculature and bone thickness.
• Octodon degus shows good mandibular performance for mid-to-strong biting, despite a relatively low bite force.
• Chinchilla lanigera's mandible demonstrated the poorest mechanical performance for biting among the studied species.

Conclusions:

• The mandibles of Ctenomys talarum and Octodon degus are better adapted to withstand strong biting forces, aligning with their digging behaviors and phylogenetic relatedness.
• The adductor musculature of Chinchilla lanigera may serve functions beyond incisor biting, given its low bite force and model-predicted stress resistance.
• Mandibular structural strength varies significantly across caviomorph species, reflecting adaptations to distinct ecological roles and behaviors.