Variable in shape: triangular (S. mokarran) or slender (S. lewini), with serrated cutting edges, thick and bulky root, and deep transverse groove.

Size: 2-15 mm.

Ecology: inhabits nearshore to offshore waters (1–300 m), coastal and oceanic, warm-temperate and tropical waters, feeding on crustaceans, fish, cephalopods, and other sharks; known to reach 6 m in length.

Geological range: Miocene-Recent.

Geographic distribution: Caribbean in fossil record; Cosmopolitan in the present day.