Raja is a genus of skates in the family Rajidae containing nearly 30 species. They are flat-bodied, cartilaginous fish with a rhombic shapes due to their large pectoral fins extending from or nearly from the snouts to the bases of their tails. Their sharp snouts are produced by a cranial projection of rostral cartilage. The mouth and gills are located on underside of the body. They may be either solid-coloured or patterned, and most skates have spiny or thorn-like structures on the upper surface, and some species contain weak electrical organs within their tails. These bottom-dwellers are active during both day and night. Skates are found in most parts of the world, from tropical to near arctic waters, from shallows to depths of more than 2,700 metres. Skates and related species have fossil records dating from the Upper Cretaceous period, thus this well adapted species is quite ancient.