Machaeridia
plural noun
Mach·ae·rid·ia
ˌmakəˈridēə
: a small group of Ordovician and Devonian animal fossils that are wormlike and bilaterally symmetrical but enclosed by plates suggesting those of echinoderms, are considered structurally comparable to the dipleurula and ancestral to modern echinoderms, being then made a class of Echinodermata, or are regarded as aberrant barnacles and included among the Cirripedia
Word History
Etymology
New Latin, from Latin machaera sword, dagger (from Greek machaira) + New Latin -idia