/ Thesaurus / H Synonyms of heterostraci Find synonyms for: Noun1. Heterostraci, suborder Heterostraci, animal orderusage: extinct group of armored jawless fishes or fish-like vertebrate; taxonomy is not clearWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: nefarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language