Family Rhinidae Müller & Henle, 1841 Type genus. Rhina Bloch & Schneider, 1801 (subsequent designation; stem thought to be first confirmed by Jordan, 1923 (van der Laan et al., 2014)). Description. Medium to large shark-like rays (adults to 3.1 m TL) with a variably depressed trunk, weakly formed disc, and a head either thickened and broadly domed (Rhina), or flattened wedge-shaped (Rhynchobatus). Pectoral fins triangular, distinct, and join to head behind eye level. Nostrils long and narrow, and usually slightly oblique; small undulate mouth with strong, rounded to oval teeth lacking distinct cusps; anterior nasal flaps poorly to moderately developed and not forming a nasal curtain. Spiracles large with no folds (Rhina), or typically with two well-developed skin folds (Rhynchobatus) along their hind margin. Tail robust, slightly longer than disc; lateral skin folds weak anteriorly but expanded posteriorly to form a broad keel on caudal peduncle and anterior caudal fin; keels extending well onto central part of caudal fin (not almost joined adjacent origin of ventral lobe of fin). Two large upright to falcate dorsal fins (first above pelvic fins); caudal fin well-developed, with a deeply concave posterior margin and long ventral lobe. Pelvic fins moderate size, apices angular, not divided into two lobes. Skin covered with minute denticles. Thorns variably developed, in series over orbit, along dorsal midline, and usually 2– 3 short rows on each shoulder; thorns on elevated ridges, very strong and horn-like in Rhina; thorns sometimes on snout. Dorsal coloration mainly yellowish to greyish brown; often covered with white spots or ocelli; often with a black pectoral marking, variably surrounded by white spots; ventral surface white, dark blotches sometimes on snout. Two genera: Rhina and Rhynchobatus, and possibly one other undescribed. Remarks. Rhinids share with sawfishes (Pristidae) characters unique within the order Rhinopristiformes, having separate pectoral fins (not joined to the body to form a disc), the first dorsal fin located well forward of the tail (above the pelvic fins), lateral skin folds on the tail forming a keel posteriorly that do not almost coalesce near origin of ventral lobe of caudal fin, and having a well-developed lobe in the caudal fin (not always fully developed in Pristis). However, rhinids lack a modified saw-like snout and while Rhina (like sawfishes) lacks spiracular folds, members of the largest genus Rhynchobatus have two folds. Rhina and Rhynchobatus are very different morphologically and as such have been frequently placed in separate families. Molecular analysis indicates that Rhina and Rhynchobatus are sister groups.

Published as part of 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), pp. 451-475 in Zootaxa 4117 (4) on pages 470-471, DOI: 10.11646/zootaxa.4117.4.1, http://zenodo.org/record/271659