PREDICTING LOCOMOTOR MODE AND PHYLOGENETIC POSITION OF AN EXTINCT PLIO-PLEISTOCENE MUSTELID WITH MORPHOMETRICS

The extinct mustelid genus Trigonictis is found in North American Pliocene and Pleistocene deposits and is represented by two species: Trigonictis macrodon and T. cookii. The placement of Trigonictis within a phylogeny of extant mustelids is uncertain. Previous work placed the genus in the subfamily Galictinae, based on dental similarities with two extant genera: Eira and Galictis. However, molecular phylogenetic work has suggested that Eira is more closely related to the Martes / Gulo clade than to any of the South American mustelids. This makes the Galictinae a questionable grouping and further confuses the issue of the placement of Trigonictis. In addition, Galictis and Eira differ in their behavior and ecology. The post-cranial element shapes of 13 species of living carnivores representing members of the superfamily Musteloidea were analyzed using principal components analysis and discriminant analysis in order to understand if locomotor habit and genus could be predicted using element shape. The data from this modern sample was used to understand the phylogenetic affiliations and locomotor patterns of the Plio-Pleistocene genus Trigonictis. The PCA demonstrates the existence of significant shape variability between genera and between locomotor groups and confirms findings based on molecular data that reject the placement of the genus Eira within the Galictinae. Discriminant analysis predictions of genus and locomotor group within the extant data set were highly accurate (above 90% in some cases). The results of the two multivariate analyses of shape indicated that the two species of Trigonictis possessed a generalized locomotor pattern and are much more similar in their post-cranial morphology to Mustela and Martes than to Galictis and Eira.