Clasper Morphology of the Japanese Sawshark, Pristiophorus japonicus Günther, 1870 (Chondrichthyes: Elasmobranchii)

Abstract

Sawsharks (Pristiophoriformes) are slender, medium-sized sharks with elongated, saw-like snouts, and include the monotypic Pliotrema and Pristiophorus with seven species. The phylogenetic position of sawsharks is still problematic as phylogenetic hypotheses based on morphological and molecular evidence disagree about their relationships, whether closer to batoids (morphological data) or grouped with squaliforms, angelsharks, and hexanchiforms in an all shark higher taxon (molecular data). However, many aspects of the morphology of sawsharks are poorly known. The present article describes the clasper musculature and skeleton of a sawshark (Pristiophorus japonicus); the clasper skeleton of a sawshark is described for the first time. The clasper musculature is similar to squaliforms and most batoids, whereas the clasper skeleton is similar to that found in Squatina and Squalus. However, the ventral marginal, dorsal terminal (dt), and ventral terminal cartilages are distinct and diagnostic at least for Pristiophorus japonicus. Comparisons with galeomorph sharks are necessary to further refine our conclusions in relation to the systematic significance of the clasper muscles and skeleton of the Japanese sawshark. Anat Rec, 302:1666–1670, 2019. © 2019 American Association for Anatomy.