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)

Anotations

Scope note:

Class of vertebrate shark-like aquatic animals characterized by having no scales, four gill pairs under one gill opening on each side, an erectile dorsal fin, in using claspers to accomplish internal fertilization of females, laying eggs with leathery cases, differing from sharks in having upper jaws that are fused to the braincase, separate anal and urogenital openings, and a few large permanent grinding tooth plates instead of teeth. In some classifications, they are included in the same class with rays and sharks.