Its 37 species are placed within the 10 genera: Gladioserratus, Heptranchias, Hexanchus, Notidanodon, Notorynchus, Pachyhexanchus, Paraheptranchias, Pseudonotidanus, Welcommia, and Weltonia.

Their excretory and digestive systems are also unspecialized, suggesting they may resemble those of primitive shark ancestors.

[3] Their most distinctive feature, however, is the presence of a sixth, and, in two genera, a seventh, gill slit, in contrast to the five found in all other sharks.

Although skeletal remains for this species have been found from the Jurassic time period, these have been very rare and have only been found in the "Late Jurassic lithographic limestones of South Germany, Nusplingen, Solnhofen, and late Cretaceous calcareous sediments of Lebanon."

Due to these sparse records some scientists conclude that the cow shark is now a more "diverse and numerous species".