Genus: Isistius, Cookiecutter Shark, Cookiecutter Sharks
lower teeth - smooth edges
Cigar-shaped body; head narrow and conical; short, bulbous snout; spiracles present, large, behind eye; no nictitating eyelids; mouth small; lips suctorial, not fringed; teeth in upper and lower jaws different, upper teeth narrow, needle-like, single points, lower teeth huge, triangular, compressed, broad, blade-like, edges smooth; 5 gill slits, all before pectoral; both dorsal fins small, close together, near tail fin, without spines, first equal or smaller that second; no anal fin; no lateral ridges between pectoral and pelvic fins; no pits on upper tail base; keel on tail base; tail fin variable from strongly asymmetrical to nearly symmetrical, terminal notch may be present.
There are three species in this genus, which has a worldwide distribution in tropical and temperate seas. One circumtropical species and one from the NW Atlantic and NW Pacific are in the western Atlantic, both of which enter shallow waters in our area.