/ak'euhn thoh"dee euhn/ , n.
any small, spiny-finned, sharklike fish of the extinct order Acanthodii, from the Paleozoic Era.
[ 1850-55; Acanthodi ( i ) pl. of ACANTHODIUS (equiv. to Acanthod ( es ) a genus ( akanthódes prickly, spiny; see ACANTH-, -ODE 1 ) + L -ius ) + -AN ]