Rhinobatidae Bonaparte, 1835

Last, Peter R., Séret, Bernard & Naylor, Gavin J. P., 2016, A new species of guitarfish, Rhinobatos borneensis sp. nov. with a redefinition of the family-level classification in the order Rhinopristiformes (Chondrichthyes: Batoidea), Zootaxa 4117 (4), pp. 451-475 : 465

Family Rhinobatidae Bonaparte, 1835

Type genus. Rhinobatos Linck, 1790 (inferred from stem).

Description. Small to large rays guitarfishes (adults attaining 1.7 m TL) with a flattened, wedge- or shovel-shaped disc with a strongly depressed trunk. Snout often elongated and its tip narrowly pointed to broadly rounded. Eyes and spiracles medium to large; spiracles with 1–2 variably developed folds. Nostrils short and very oblique (with fewer than 62 lamellae), nasal curtain absent; anterior nasal flaps often very broad (almost joined mesially), inserted close to inner edge of nostril, or insertions extending slightly into internasal space (to level of nostril inner corner). Mouth profile straight to lower jaw weakly convex. Skin usually covered with fine denticles (sometimes partly naked); small thorns and thornlets variably developed in row along dorsal midline of body, in small patches near eyes, and on shoulder and snout. Pelvic fins long-based, positioned laterally and posteriorly to the disc. Tail not especially robust, depressed, with well-developed lateral skin folds extending along its ventrolateral margin; folds almost united on caudal-fin base near origin of ventral lobe of caudal fin. Two dorsal fins well separated, first positioned well to slightly behind rear tips of pelvic fins. Caudal fin small, lacking an obvious ventral lobe. Dorsal coloration plain (usually greyish or brownish) or with strong pattern of lines, bars, spots and/or blotches; edges of cranium and rostral cartilage not usually sharply demarcated with snout; ventral surface usually white, black blotch often present on snout. Three genera: Acroteriobatus , Rhinobatos and Pseudobatos .

Remarks. Pseudobatos undoubtedly represents a valid genus-level taxon but is not fully resolved as its familial assignment needs further investigation based on its apparent polyphyly with other genera based on molecular data. Relatively poorly developed nasal flaps in members of this amphi-American group is shared with Rhinobatos rhinobatos , the type species of the genus ( Indo –Pacific Rhinobatos typically have larger flaps, most strongly expressed by the posterior nasal flap, which is broad and can extend almost to the innermost corner of the nostril). Rhinobatos is sister to Acroteriobatus but paraphyletic to the Indo –Pacific Rhinobatos . The anterior nasal flaps of Acroteriobatus , which are almost joined in the medial region of the internasal space and well anterior of the innermost corners of the nostrils, are among the most well-developed of rhinopristiforms. The trygonorrhinid genus Aptychotrema has anterior nasal flaps inserted more posteriorly in the internasal space.