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
Slender smooth-hound numerous unique traits. More recently, he and other taxonomists have increasingly tended to group "Gollum" and "Pseudotriakis" together in the family Pseudotriakidae. This arrangement was corroborated by a 2006 phylogenetic study by Juan Andrés López and colleagues, which found that the two genera have a high degree of genetic similarity across four protein-coding genes and form a natural clade apart from "Proscyllium". An additional species of "Gollum" has now been described, and there is at least one additional species yet to be described. The range of the slender smooth-hound is restricted to the upper and middle continental slope around New