Familia Rajidae

Rajidae

by M. Stehmann and D. L. B├╝rkel

Small moderate or large rays (from about 30 to 200 cm TL), the head, body and greatly enlarged pectoral fins strongly depressed as a rhomboid to at times subcircular disc, the tail moderately slender and very distinct from disc, with a narrow fold along each side. Snout ranging from obtusely rounded to acutely pointed; soft and flexible in some species, stiff and inflexible in others (depending on condition of rostral cartilage and forward extension of pectoral finrays (see key to genera)). Mouth straight to moderately curved; numerous small, single-cusped teeth in bands, forming a pavement or parallel rows (or a combination of the two), the teeth flat to pointed, often different in the two sexes. Nostrils small, close in front of mouth, their inner margins expanded back to mouth as a nasal curtain, where they are joined by a transverse isthmus in front of the mouth. Spiracles immediately behind eyes, with pseudobranchial folds at anterior walls. Pectoral fins greatly enlarged, fused completely to sides of head and trunk, from snout to insertion of pelvic fins; pelvic fins bilobed, but with a joint outer margin; two small dorsal fins, about equal in size and shape, set far back on tail; caudal fin rudimentary, a low fold only behind second dorsal fin. Upper surfaces sparsely to densely covered with prickles and small and/or distinct thornlets and thorns, the latter in a pattern of patches, rows or singly in certain areas (apart from the special claw-like 'alar' thorns near the wing-tips of maturing males, which usually also have 'malar' thorns on each side of the head at the level of the eyes; these are not taken into account in the key to species); at least a median row of thorns along tail, except in the subgenus (Malacoraja) of Raja; underside smooth to more or less prickly, but also some irregular thorns in a few species. Colours and patterns various.
Benthic from inshore waters (where common) to abyssal depths in all oceans from Arctic to Antarctic latitudes, occasionally in brackish water, less common in shallow tropical waters, absent from tropical coral reef areas; of commercial importance in some places. Feeding on all kinds of bottom animals. Oviparous; large horny rectangular egg-cases, with two short horns at one end and two longer horns at the other, deposited on the bottom. Long migrations in larger deepwater species.

Recent revisions: Bigelow and Schroeder (1953), Ishiyama (1958), Stehmann (1970, 1976), Hulley (1970, 1972), among others, all on a regional basis.

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