Humpback smooth-hound the lower ones. The teeth have a main pointed cusp and sometimes smaller subsidiary ones. The first dorsal fin is approximately triangular and the trailing edge is fringed with bare, dark-coloured collagen rods known as ceratotrichia. The pectoral fins are large and the pelvic fins moderately so. The caudal peduncle is short and the lower lobe of the tail fin is hardly curved in adults. The colour of this shark is plain grey or greyish-brown without any spots or barring. The humpback smooth-hound is found in the eastern Pacific Ocean off the coast of Peru and Chile, between 1°N and
Spotless smooth-hound continental shelf and in semi-enclosed areas of sea at depths down to and possibly as deep as . It is found near the seabed, often over sandy substrates and is thought to feed on crustaceans and other benthic invertebrates. The spotless smooth-hound is viviparous. Males become sexually mature at a length of between and females at . Litter size varies between about five and sixteen pups which are nourished by yolk sac placentas. The gestation period is about ten months and the pups measure about at birth. Maximum recorded age is nine years. The spotless smooth-hound is used for human