The forelimbs of Octodontidae (Rodentia: Mammalia): substrate use, morphology, and phylogenetic signal

Rodents of the family Octodontidae, endemic to South America, represent a group with low taxonomic richness group (six genera and 14 species) but have great ecomorphological diversity with epigean, semi-fossorial, fossorial, and subterranean forms. We analyzed morphometric variation in humerus and ulna, the possible relationship with substrate preference use, and the presence of a phylogenetic signal in the forelimbs traits (five biomechanical indices). Our results show that, in octodontids, the forelimb variation was not primarily associated with their phylogeny and some attributes are highly explanatory in terms of function, with a clear differentiation between the substrate use gradient extremes (i.e. epigean and subterranean forms). The two forelimb traits, the development of humeral epicondyles and the olecranon process of the ulna, indicative of adaptive trends found in Octodontidae are consistent with most of those described for other mammals and corroborate the relevance of forelimb characters to differentiate modes of locomotion or substrate preferences.

Automated summary

The research found that in octodontids, variations in forelimb features were not primarily associated with phylogeny, but were highly explanatory in terms of function, effectively distinguishing between animals living in epigean and subterranean habitats. Specific features observed in the humerus and ulna indicated adaptive trends in octodontids similar to those found in other mammals.