Dusky smooth-hound fishes is their ability to continually replace the teeth in their upper and lower jaws. Smooth dogfish differ from other sharks because of their 10 rows of flat, blunt teeth. The teeth in the upper and lower jaws are similar in size and are asymmetrical with rounded cusps. These teeth are used to crush and grind food, rather than bite it. Their unique dentition is important for their crustacean-based diet. In smooth dogfish, tooth replacement is related to body growth. They grow about 10 cm per every six rows of teeth replaced. That is an increase of 0.03 mm per
Speckled smooth-hound peduncle is short and the lower lobe of the tail fin is narrow and slightly curved. The maximum length is about with maturity being reached by males at about and females at about . Adults are grey or greyish-brown above and paler below, liberally speckled with white spots. Juveniles have dark bars. The speckled smooth-hound is found off the Pacific coast of South America, including the Galapagos Islands and the Juan Fernández Islands. Its range extends from the Isla Lobos de Tierra in Peru to the southern tip of Chile. It is a demersal fish and swims close to the