Ulnar dimensions and fossoriality in armadillos

Ulnar dimensions were measured in 14 species of armadillos (Xenarthra: Dasy podidae). An index of fossorial ability (IFA) was constructed, relating the length of the olecranon process to the remaining length of the ulna. For c omparative purposes, the same measurements were taken in 14 other species o f mostly South American mammals belonging to 3 orders and 11 families. The fossorial habits of these mammals were classified into 3 categories: (1) sp ecies mostly cursorial and non-digging; (2) species that often dig, but to which digging plays no essential part in their alimentary strategy and are not burrowers; and (3) species that are burrowers. IFA means of the studied mammal orders were compared using one-way analysis of variance on log-tran sformed data. Bivariate size allometry between ulnar dimensions and body ma ss was assessed by fitting (least squares and geometric mean) linear regres sions of log-transformed data. It is concluded that the IFA discriminates a mong the species according to their fossorial habits within orders, but it is not equally useful in distinguishing fossorial species between orders. I n armadillos, the relationships between ulnar dimensions and body mass are isometrical. Finally, the IFA is independent of body size.