Common smooth-hound on its underneath. It is often confused with the starry smooth-hound which has white spots on its back. The starry smooth-hound can often have faded spots which leads to misidentification. Another shark it is often confused with is the tope shark although the common smooth hound has a larger second dorsal fin. Due to the similarities between the common smooth-hound and other sharks, misidentification occurred for a long time. The common smooth-hound has two dorsal fins, an anal fin, a pair of pectoral fins, a pair of pelvic fins and a heterocercal tail. All of these fins help stabilise the
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