Definition of Acanthodii
: a subclass of Placodermi comprising primitive Paleozoic fishes having the anterior margin of each fin supported by a stout spine and often having one or more pairs of spines similar to the fin spines along the lower lateral part of the body between the paired fins of each side
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Origin and Etymology of acanthodii
New Latin, from Acanthodes
First Known Use: 1851
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