Skeletal indicators of locomotor adaptations in living and extinct rodents.
Living rodents show great diversity in their locomotor habits, including semiaquatic, arboreal, fossorial, ricochetal, and gliding species from multiple families. To assess the association between limb morphology and locomotor habits, the appendicular skeletons of 65 rodent genera from 16 families were measured. Ecomorphological analyses of various locomotor types revealed consistent differences in postcranial skeletal morphology that relate to functionally important traits. Behaviorally similar taxa showed convergent morphological characters, despite distinct evolutionary histories. Semiaquatic rodents displayed relatively robust bones, enlarged muscular attachments, short femora, and elongate hind feet. Arboreal rodents had relatively elongate humeri and digits, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. Fossorial rodents showed relatively robust bones, enlarged muscular attachments, short antebrachii and digits, elongate manual claws, and reduced hind limb elements. Ricochetal rodents displayed relatively proximal insertion of muscles, disproportionate limbs, elongate tibiae, and elongate hind feet. Gliding rodents had relatively elongate and gracile bones, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. The morphological differences observed here can readily be used to discriminate extant rodents with different locomotor strategies. This suggests that the method could be applied to extinct rodents, regardless of ancestry, to accurately infer their locomotor ecologies. When applied to an extinct group of rodents, we found two distinct ecomorphs represented in the beaver family (Castoridae), semiaquatic and semifossorial. There was also a progressive trend toward increased body size and increased aquatic specialization in the giant beaver lineage (Castoroidinae).
Samuels
Joshua X
JX
Department of Ecology and Evolutionary Biology, University of California-Los Angeles, Los Angeles, California 90095, USA. jsamuels@ucla.edu
Van Valkenburgh
Blaire
B
D000222:Adaptation, Physiological; D000704:Analysis of Variance; D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D050281:Bones of Lower Extremity / Q000033:anatomy & histology*; D001133:Bones of Upper Extremity / Q000033:anatomy & histology*; D016002:Discriminant Analysis; D005260:Female; D005269:Femur / Q000033:anatomy & histology; D005580:Fossils; D006811:Humerus / Q000033:anatomy & histology; D016014:Linear Models; D008297:Male; D050279:Metacarpal Bones / Q000033:anatomy & histology; D008682:Metatarsal Bones / Q000033:anatomy & histology; D009043:Motor Activity / Q000502:physiology; D011884:Radius / Q000033:anatomy & histology; D012044:Regression Analysis; D012377:Rodentia / Q000033:anatomy & histology* / Q000502:physiology; D013977:Tibia / Q000033:anatomy & histology; D050277:Toe Phalanges / Q000033:anatomy & histology; D014457:Ulna / Q000033:anatomy & histology