Squalomorphii

Squalomorphii; Temporal range: 170–Recent Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Spiny dogfish
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Superorder:	Squalomorphii; Compagno 1973
Orders
	Hexanchiformes; Squaliformes; Squatiniformes; Pristiophoriformes; †Protospinax (unplaced in order);

Squalomorphii is a

Pristiophoriformes

.

Classification

Order Hexanchiformes

The order Hexanchiformes is a very small and primitive order consisting of cow sharks and frilled sharks. These sharks have only 1 dorsal fin, 6-7 gill slits, and no nictitating membrane on the eyes. Cow sharks are fairly large and stocky, while frilled sharks are smaller and have eel-like bodies. The oldest fossils from this order can be dated back to the mid-Jurassic.^[1]

There are six living species in 4 genera, and 2 families.

Family
Hexanchidae
(Cow sharks)
Family Chlamydoselachidae (Frilled sharks)

Order Squaliformes

The order Squaliformes is a large, ancient order of sharks. Sharks from this order have two dorsal fins -usually with spines-, no anal fin, and no nictitating membrane on the eyes. Squaliform sharks are extremely variable in size and shape, and can be found in most marine habitats throughout the world. Like Hexanchiformes, members of Squaliformes can be found as early as the Jurassic period.^[2]

There are around 126 species in 23 genera, and 7 families.

Family Centrophoridae (Gulper sharks)
Family Dalatiidae (Kitefin sharks)
Family
Echinorhinidae
(Bramble sharks)
Family Etmopteridae (Lantern sharks)
Family
Oxynotidae
(Rough sharks)
Family Somniosidae (Sleeper sharks)
Family Squalidae (Dogfish sharks)

Order Squatiniformes

The order Squatiniformes is a small order of highly specialized and recognizable sharks called angel sharks. The angel sharks have flattened bodies and broad pectoral fins, as well as camouflaged coloration. These characteristics allow angel sharks to blend in with their

benthic environments. Members of Squatiniformes have been found since the late Jurassic period.^[3]

There are 23 species in 1 genus, and 1 family.

Family
Squatinidae
(Angel sharks)

Order Pristiophoriformes

The order Pristiophoriformes is a small order of unique sharks called sawsharks. Sawsharks have a long snout covered in teeth, between 5-6 gill slits, and no anal fin. They also have a pair of barbels usually located halfway down the snout. Sawsharks are frequently confused with sawfish, which are members of the ray order

ventral gill slits. These sharks can mostly be found in deep benthic environments. Fossils of members of this order have been found since the late Jurassic period.^[4]

There are 8 species in 2 genera, and 1 family.

Family
Pristiophoridae
(Saw sharks)

References

^ Compagno, Leonard. Sharks of the World. Princeton: Princeton UP, 2005. Print.
^ Compagno, Leonard. Sharks of the World. Princeton: Princeton UP, 2005. Print.
^ Froese, Rainer, and Daniel Pauly, eds. (2009). "Squatinidae" in FishBase. January 2009 version.
^ Froese, Rainer, and Daniel Pauly, eds. (2013). "Pristiophoridae" in FishBase. October 2013 version.