of rays known as the wedgefishes that also have large, shark-like fins. Morphological analyses have tended to place these two genera basally among rays, though some have them as basal to just the guitarfishes (Rhinobatidae) and skates (Rajidae) while others have them basal to all other rays except sawfishes (Pristidae). A 2012 study based on mitochondrial DNA upheld Rhina and Rhynchobatus as sister taxa related to the guitarfishes, but also unexpectedly found that they formed a clade with the sawfishes rather than the skates. Following the description of Rhynchorhina in 2016, a study of mtDNA found that it is part of the same group and their phylogenetic relationship is ((Rhynchobatus+Rhynchorhina)+Rhina). In terms of classification, Bloch and Schneider originally placed the bowmouth guitarfish in the order Abdominales, a now-obsolete grouping of fishes defined by the positioning of their pelvic fins directly behind the pectoral fins. Modern sources have included it variously in the order Rajiformes, Rhinobatiformes, Rhiniformes, or the newly proposed Rhinopristiformes. The placement of the bowmouth guitarfish in the family Rhinidae originates from the group "Rhinae", consisting of Rhina and Rhynchobatus, in Johannes Müller and Jakob Henle's 1841 Systematische Beschreibung der Plagiostomen. Later authors have also assigned this species to the family Rhinobatidae or Rhynchobatidae. Joseph Nelson, in the 2006 fourth edition of Fishes of the World, placed this species as the sole member of Rhinidae in the order Rajiformes, which is supported by morphological but not molecular data. More recent authorities have placed it in Rhinidae together with Rhynchobatus and Rhynchorhina, reflecting both genetic data and the morphologically intermediate position of Rhynchobatus between Rhina and Rhynchorhina. Description Rhina ancylostoma is a heavily built fish growing to long and in weight. The head is short, wide, and flattened with an evenly rounded snout; the front portion of the head, including the medium-sized eyes and large spiracles, is clearly distinct from the body. The long nostrils are transversely oriented and have well-developed skin flaps on their anterior margins. The lower jaw has three protruding lobes that fit into corresponding depressions in the upper jaw. There are around 47 upper and 50 lower tooth rows arranged in winding bands; the teeth are low and blunt with ridges on the crown. The five pairs of ventral gill slits are positioned close to the lateral margins of the head. The body is deepest in front of the two tall and falcate (sickle-shaped) dorsal fins.