A new synapomorphy in the pelvic girdle reinforces a close relationship of Zanobatus and Myliobatiformes (Chondrichthyes: Batoidea)

Abstract

The rays of the order Myliobatiformes present several diagnostic characters, the most striking one being the presence of a serrated sting on the dorsal region of the tail. Although several morphological hypotheses have been proposed supporting the monophyly and interrelationships of its members, few characters of the appendicular skeleton were employed. In the present study, we analyzed comparatively the pelvic girdle morphology across all the groups of rays to investigate the distribution of the ischial process. To understand its significance, we tested this character of the pelvic girdle as a potential synapomorphy for the Myliobatiformes plus Zanobatus. Accordingly, the phylogenetic position of Zanobatus as a sister taxon to Myliobatiformes is reinforced and its pelvic girdle morphology reinterpreted in relation to previous morphological studies.