An ecomorphological analysis of forelimb musculotendinous system in sigmodontine rodents (Rodentia, Cricetidae, Sigmodontinae)

The central tenet of ecomorphological theory holds that there is a correlation between design (morphological traits) and ecology of organisms. The sigmodontine rodents (Rodentia, Cricetidae, Sigmodontinae) exhibit a remarkably high diversity of locomotory types, allowing them to occupy different environments and ecological niches. The main aims of our work were to test whether the internal morphology of the forelimb of 26 species of sigmodontines, as assessed through the analysis of 32 characters, differs among taxa that exhibit different types of locomotion (saltatorial, ambulatory, fossorial, scansorial, and natatorial), and whether such patterns also can be explained by the phylogenetic affinities of the species examined. Our results show that phylogeny explains an important part of the observed morphological variation in sigmodontine rodents. This phylogenetic inertia could be responsible for the homogeneity in the overall muscle forelimb morphology in this group. Tendon variables seem to be better descriptors of locomotory types than muscule variables. Twelve tendon variables of the forelimb exhibit distinct differences between fossorial and scansorial sigmodontines. No particular morphological variables are associated with ambulatory, saltatorial, and natatorial taxa. Additionally, 3 muscles (triceps longus, extensor digitorum, and flexor digitorum profundus) exhibit a greater anatomical cross-sectional area in fossorial and natatorial taxa than in other locomotory types.