The devil is in the details: identification of postcranial elements of Canis dirus and Canis lupus from Rancho La Brea using discriminant function and morphometric analyses (919.7)

Abstract

The preservation of fossils in the tar pits at Rancho La Brea makes identification of postcranial material difficult, especially separating Canis lupus form Canis dirus. Generally, distinguishing C. dirus from C. lupus is achieved by study of the dentition and cranial features; otherwise most postcranial bones are identified by size. Because the tar pits at Rancho La Brea disarticulate the remains during the fossilization process, one bony element can rarely be associated with any other. Therefore, another means of identification is needed for postcranial canid materials. I compiled a series of measurements of scapulae, humeri, and ulnae of C. dirus to compare with similar measurements of modern C. lupus. The wolf specimens in this study represent wild populations of North American subspecies that often included sex and age information. By comparing linear measurements of both taxa, I was able to determine statistically relevant differences in the forelimb bone using discriminant function analysis and morphometrics. Being able to provide composite size ranges for individual bony elements, these disarticulated canid specimens of C. dirus and C. lupus can be more accurately identified only from postcranial material. These comparisons can serve as a reference tool for accurately comparing other fossil canid specimens as well as modern species when cranial material is unavailable.