ˌ ̷ ̷ ̷ ̷ˈärkə noun plural
Usage: capitalized
Etymology: New Latin, from anti- (I) + -archa (from Greek archos anus); from the contrast in the location of the anus with that of the Urochorda
: a subclass or other division of Placodermi comprising small Devonian freshwater ostracoderms having complex bony armor on the anterior part of the body and a pair of pectoral appendages resembling paddles