Comparative anatomy of the clasper of catsharks and its phylogenetic implications (Chondrichthyes: Carcharhiniformes: Scyliorhinidae).

The presence of claspers is one of the main characteristics of the cartilaginous fishes, but its variations across taxa have received limited use in shark systematics and have generally been neglected in descriptions of species. Clasper descriptions are available only for a few catshark species and most of these are focused only in external morphology. Besides that, divergences regarding the identification of some structures persist in the literature emphasizing the need of more encompassing morphological comparative analyses on claspers of scyliorhinids. In this study, claspers structures of almost all catshark genera were examined, described, and illustrated (except Akheilos and Pentanchus) and comments on their phylogenetic significance are provided. Some characters such as degree of development of rhipidions and terminal dermal cover, occurrence, position and size of accessory marginal and terminal cartilages proved to be useful for taxonomic purposes and their significance along carcharhiniforms systematics needs to be further investigated. RESEARCH HIGHLIGHTS: Clasper morphology of catsharks is described and compared and its systematic significance is discussed here. External morphology and skeleton components of claspers vary widely among scyliorhinids and may be useful in phylogenetic analyses.