Rhina ancylostoma, the bowmouth guitarfish, shark ray or mud skate, is a species of ray and a member of the family Rhinidae. Its evolutionary affinities are not fully resolved, though it may be related to true guitarfishes and skates. This rare species occurs widely in the tropical coastal waters of the western Indo-Pacific, at depths of up to . Highly distinctive in appearance, Rhina ancylostoma has a wide and thick body with a rounded snout and large shark-like dorsal and tail fins. Its mouth forms a W-shaped undulating line, and there are multiple thorny ridges over its head and back. It has a dorsal color pattern of many white spots over a bluish gray to brown background, with a pair of prominent black markings over the pectoral fins. This large species can reach a length of and weight of . Usually found near the sea floor, Rhina ancylostoma prefers sandy or muddy areas near underwater structures. It is a strong-swimming predator of bony fishes, crustaceans, and molluscs. This species gives live birth to litters of two to eleven pups, which are nourished during gestation by yolk. The International Union for Conservation of Nature (IUCN) has assessed Rhina ancylostoma as Vulnerable because it is widely caught by artisanal and commercial fisheries for its valuable fins and meat. It is viewed as a nuisance by trawlers, however, because its bulk and thorny skin cause it to damage netted catches. Habitat degradation and destruction pose an additional, significant challenge to this ray's survival. Rhina ancylostoma adapts well to captivity and is displayed in public aquariums. Taxonomy and phylogeny German naturalists Marcus Elieser Bloch and Johann Gottlob Schneider described Rhina ancylostoma in their 1801 Systema Ichthyologiae. Their account was based on a long specimen, now lost, collected off the Coromandel Coast of India. The genus name Rhina comes from the Greek rhinos ("snout"); the specific epithet ancylostoma is derived from the Greek ankylos ("curved" or "crooked") and stoma ("mouth"). Although Block and Schneider wrote the epithet as ancylostomus and that form appears in some literature, most modern sources regard the correct form to be ancylostoma. Other common names for this species include shark ray, mud skate, shortnose mud skate, bow-mouthed angel fish, and bow-mouthed angel shark. The evolutionary relationships between Rhina ancylostoma and other rays are debated. Morphological evidence generally points to a close relationship between Rhina, Rhynchobatus and Rhynchorhina, which are a group