Hexanchiformes

Frilled shark ( Chlamydoselache anguineus ). Drawing from the report of the Challenger expedition, Günther 1887

As Hexanchiformes refers to a quite primitive order of sharks, consisting of two families with a total of six species. The animals are sometimes referred to in English as Grauhaiartige or Kammzähnerhaie, sometimes the term collar sharks is used, but this is also one of the families included.

Typical of the sharks this order of possession is a single, spineless dorsal fin; In contrast to other systems of Squalea (eg Dornhaiartigen and rays) they have a anal fin. Unlike other shark species, which are usually equipped with five gill slits that have Hexanchiformes six or seven.

System

The order is divided into two families:

• The collar sharks ( Chlamydoselachidae ) in the strict sense, sometimes referred to as Krause sharks include the types Chlamydoselachus anguineus and Chlamydoselachus africana.
• The Kammzähnerhaie ( Hexanchidae ), also called gray sharks, include four species in three genera. However, the term " gray sharks " is ambiguous and sometimes also for the requiem sharks ( Carcharhinidae ), an unrelated family from the order of ground sharks ( Carcharhiniformes ) used.