Higher elasmobranch phylogeny and biostratigraphy

Abstract

Living sharks, skates and rays share several derived skeletal characters that are absent in most extinct elasmobranchs, suggesting a monophyletic group of ‘higher’ elasmobranchs. Within this group opinions vary as to phylogenetic relationships, although three broad groups are generally recognized. Arguments for and against monophyly of these group (batoids; squalomorphs; galeomorphs) are examined. Many of their contained taxa are also of questionable validity. Cladistic analysis of living galeomorphs reveals a sequence of characters supporting monophyly of the group as whole, but not of its more generalized contained taxa. The temporal distribution of fossil galeomorphs corroborates the hypothesis of relationship suggested by neontological data; i.e. there is considerable stratigraphic harmony with Recent phylogenetic data.