Hierarchy classification:

1. top of the aat hierarchies
2. Agents Facet
3. Living Organisms (hierarchy name)
4. living organisms (entities)
5. Eukaryota (domain)
6. Animalia (kingdom)
7. Chordata (phylum)
8. Vertebrata (subphylum)
9. Chondrichthyes (class)
10. Elasmobranchii (subclass)

Anotations

Scope note:

Members of an order containing 400 living species and many fossil species of predatory, cartilaginous fishes that have a fusiform shape and gill cleft location on either side of the head resembling bony fishes; most having a tough skin that is dull gray in color and roughened by toothlike scales; a muscular, asymmetrical, upturned tail and pointed fins; a pointed snout extending forward and over a crescentic mouth set with sharp triangular teeth; and a lack of a swim bladder requiring the animals to swim nearly perpetually to keep from sinking to the bottom. A few of the larger species are able to maintain their body temperature above the surrounding water temperature, although they are not truly warm blooded. Sharks developed as long ago as 450 million years ago. Some classifications place sharks in the superorder Selachimorpha.