Cranial morphology and dietary habits of rodents

TLDR

Rodents are ecologically diverse and abundant across terrestrial ecosystems, yet their ecomorphology is poorly documented, leading to their underrepresentation in palaeoecological studies. The study uses geometric and linear morphometrics to investigate how cranial and dental morphology reflects the diets of living rodents. Geometric and linear morphometrics were applied to cranial and dental measurements of living rodent species to assess diet‑related shape variation. The analysis revealed that rodents with similar diets exhibit convergent cranial and dental morphology—carnivores have elongated incisors and reduced cheek tooth areas, insectivores display degenerate dentition and elongated rostra, herbivores possess broader incisors and larger cheek tooth areas—allowing accurate inference of extinct rodent diets, as shown by herbivorous diets inferred for most extinct beavers.

Abstract

Rodents are important components of nearly every terrestrial ecosystem and display considerable ecological diversity. Nevertheless, a lack of data on the ecomorphology of rodents has led to them being largely overlooked in palaeoecological reconstructions. Here, geometric and linear morphometrics are used to examine how cranial and dental shapes reflect the diets of living rodent species. Although most rodents are omnivores or generalist herbivores, some species have evolved highly specialized carnivorous, insectivorous, and herbivorous diets. Results show that living rodents with similar diets display convergent morphology, despite their independent evolutionary histories. Carnivores have relatively elongate incisors, elongate and narrow incisor blades, orthodont incisor angles, reduced cheek tooth areas, and enlarged temporal fossae. Insectivores display relatively degenerate dentition, elongate rostra, narrow and thin zygomatic arches, and smaller temporal fossae. Herbivores are characterized by relatively broader incisor blades, longer molar tooth rows, larger cheek tooth areas, wider skull and rostrum, thicker and broader zygomatic arches, and larger temporal fossae. These results suggest that cranial and dental morphology can be used to accurately infer extinct rodent diets regardless of ancestry. Application to extinct beavers suggests that most had highly specialized herbivorous diets.