​There are eight distinct orders of sharks

​

Hexanchiformes:               Frilled, Sixgill & Sevengill Sharks. All have 6 or 7 gills (all other species have 5). Single spineless dorsal and anal fins. 2 families.​

Squaliformes:                   Dogfish or Dogsharks. No anal fin. Two dorsal fins (often with spines). 7 families.

​Heterodontiformes:           Hornsharks or Bullhead Sharks. Anal fin present, both dorsal fins have spines. 1 family.

​Orectolobiformes:             Carpetsharks. Anal fin, two spineless dorsal fins. Barbels on nostrils. 7 families

​Lamniformes:                   Mackerel Sharks. Anal fin, two spineless dorsal fins, mouths reach back behind eyes, no nictitating eyelid. 7 families.

​Carcharhiniformes:           Groundsharks. Anal fin, two spineless dorsal fins, mouths reach back behind eyes, nictitating eyelid. 8 families.

​Squatinaformes:               Angelsharks. No anal fin, two dorsal fins without spines set well back near the tail. Flattened ray-like body. 1 family.

​Pristiophoriformes:           Sawsharks. Sawsharks are distinctive with a long snout edged with sharp, straight teeth. 1 family.​

 

Source: http://www.marinethemes.com/sharksharkinfo.html.

Figure: Overview over the different groups of shark species