A new species of guitarfish, Rhinobatos borneensis sp. nov. with a redefinition of the family-level classification in the order Rhinopristiformes (Chondrichthyes: Batoidea).

A new guitarfish, Rhinobatos borneensis sp. nov., is described from material collected at fish markets in Malaysian Borneo (South China Sea). This ray, which is almost plain coloured with faint orange blotches in adults, has a more colourful embryo marked with small pale ocelli with dark centres. Confused with R. schlegelii (Japan to Taiwan) and its junior synonym R. formosensis, new molecular data suggests it is more closely related to a subgroup of Rhinobatos from the Indo-Malay Archipelago that includes R. jimbaranensis, R. sainsburyi and R. whitei. Based on evidence from recent phylogenetic studies, the genus Rhinobatos is non-monophyletic, nor is the Rhinobatidae a monophyletic family-level group. Former subgenera of Rhinobatos, Acroteriobatus and Glaucostegus, are valid genus-level taxa supported by both morphological and molecular evidence. Moreover, amphi-American members of Rhinobatos, assigned herein to a new genus Pseudobatos, are not monophyletic with Rhinobatos, Acroteriobatus and Glaucostegus and its position within the newly erected order Rhinopristiformes needs to be reassessed. Several molecular studies have suggested that the family Rhinobatidae is polyphyletic and needs to be redefined. We propose a revised classification of the order Rhinopristiformes based on molecular analyses and supported by morphological data, making strong use of oronasal morphology. The group now contains 5 family-level taxa: three valid nominal taxa, Pristidae (2 genera, 5 species), Rhinidae (incorporating Rhynchobatidae, 2 genera, 9 species), Rhinobatidae (3 genera, 31 species); and two new taxa, Glaucostegidae (single genus, 6 species) and Trygonorrhinidae (3 genera, 8 species).