ABSTRACT
While our primary goal is to understand the pattern of diversification that gave rise to modern elasmobranchs, we anticipate that the phylogeny we present will provide a framework that can be used to better estimate the suHe of traits that characterize the ancestral vertebrate condition. We caution, however, that this goal is possible only to the extent that the sampled diversity of modern elasmobranchs arises from evenly spaced cladogenesis from the vertebrate ancestral condition to the present day. To the extent that cladogenesis is "clumped" over time, or worse yet, is restricted to a relatively recent radiation near the tips of the tree, it may be impossible to accurately determine the vertebrate ancestral condition.
