T-shape; narrow unserrated crown perpendicular to the root; and flat roots. They can also have a slightly curved, inclined crown, elongated root lobes, and strongly obtuse basal root angle.
Size: 3-15 mm.
Ecology: inhabits tropical and temperate estuarine and intertidal-offshore (0–92 m) waters, feeding on bottom-dwelling bony fishes; known to reach 2-3 m in length.
Geological range: Miocene-Recent.
Geographic distribution: Caribbean and Pacific in fossil record and in the present day.