Analysis of the upper forelimb of Canis dirus to determine physical characteristics that might suggest sociality

Canis dirus guildayi, or the Western Dire wolf, was the most common predator at Rancho La Brea and is believed to be social as are modern wolves. In this study, the upper forelimb, specifically the scapula, humerus, and ulna of C. dirus were examined. Maps determined from examination of ridges, rugosities and other features reflecting alteration of bone surfaces by muscle attachments were created. Interpretation of significance of muscle scars on these bones was made possible by comparison to dissections of the forelimb musculature of Canis latrans (American coyote) and Urocyon cinereagenteus (Red Fox). The dire wolf is considered a social predator, in part from previous studies that characterized specific healed or partially healed skeletal injuries that parallel those in social modern wolves hunting large prey in groups. Further support for sociality in Dire wolves that also specialized in capture of large prey is suggested by anteroposterior scapular lengthening in some larger individuals. This shape, surface area and muscle scar position allowed for a relatively larger origin of the M. serratus ventralis, a muscle that supports the trunk, assists with inspiration and moves the trunk and the scapular region anteroposteriorly. This capability would allow for increased anteroposterior movement of the limb, an advantage for a pursuit predator cursor hunting in cooperation with conspecifics to capture large prey. Grant Funding Source : Northern Illinois University