Selachii

plural noun
Se·​la·​chii | \ -kēˌī\

Definition of Selachii

in some classifications
: a variously delimited group of elasmobranch fishes:
a : a primary division of Pisces that includes all the elasmobranchs and is equivalent to Chondrichthyes
b : a class or subclass that includes all the elasmobranchs except the chimaeras
c : a subclass or order that includes the existing sharks and rays as distinguished from the extinct Pleuropterygii and Ichthyotomi
d : a suborder that includes the existing sharks as distinguished from the rays and is equivalent to Pleurotremata

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History and Etymology for Selachii

New Latin, irregular from selachos cartilaginous fish; akin to Greek selas light, brightness

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