ABSTRACT
The vertebral ossicles of the ophiuroid arm form articulating joints with a complex morphology. In several ophiuroid taxa vertebral ossicle morphologies have been linked to unique arm functions (i.e., swimming) or specific ecological roles. The functional interpretation of vertebral variation remains largely speculative, however, and the range of variation in this skeletal element has only been described qualitatively. Taxa in the order Ophiurae are characterized by a zygospondylous vertebral articulation. To investigate inter-and intraspecific differences in this group I have quantified the vertebral morphology of 22 species (representing 7 families) using a set of morphometric landmarks. Correlated differences in landmark locations within and among species were investigated using principal components analysis. A multivariate approach to the ophiuroid arm skeleton thus allows functionally important variation in hard and soft structures to be quantified and rigorously compared among species.
