An animal of a group characterized by teeth attached to the jaw by roots: †(a) a reptile of the former order Rhizodonta, comprising crocodilians and their fossil relatives (obsolete); (b) a fish of the extinct family Rhizodontidae of rhipidistian fishes having sharp, rooted teeth.
Originally: of or relating to the possession of teeth attached to the jaw by roots. In later use: specifically of or relating to the extinct fish family Rhizodontidae.
Mid 19th century; earliest use found in Louis Agassiz (1807–1873), zoologist and geologist. From rhizo- + -odont, after scientific Latin Rhizodonta, former order name.