Hemichordatan.
/ˌhɛmɪkɔːˈdeɪtə/, U.S. /ˌhɛməkɔrˈdɑdɑ/, /ˌhɛməkɔrˈdeɪdɑ/ Zoology.
With plural agreement: a phylum of marine invertebrates comprising chiefly the acorn worms (class Enteropneusta), whose body consists of three parts (proboscis, collar, and trunk with gill slits) and contains a notochord-like structure, and also some colonial forms (the pterobranchs and the extinct graptolites). Also: animals of this phylum (collectively or individually); hemichordates.The Hemichordata were formerly included within the phylum Chordata but were removed when the homology of the notochord came into doubt. They were sometimes placed in a group Protochordata and are still regarded informally as ‘protochordates’.
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the world > animals > invertebrates > subkingdom Metazoa > grade Triploblastica or Coelomata > phylum Hemichordata > [noun]
Hemichordata1889
1889 Proc. Amer. Philos. Soc. 26 553 The notochord of all vertebrates, ascidians and Hemichordata.
1919 Amer. Naturalist 53 147 The lines of development of the Hemichordata and of the worm-like forms have an ultimately common ancestry.
1940 G. S. Carter Gen. Zool. Invertebr. xiv. 267 The Hemichordata have other methods of feeding.
1977 Amer. Zool. 17 35/2 Coelom formation in the Phoronida has parallels in deuterostomic phyla such as the Hemichordata.
2002 G. M. Eberhart Mysterious Creatures I. 247/2 In the Phylum Hemichordata (acorn worms), the giant acorn worms are the undiscovered adults of a known species of larvae.
This entry has been updated (OED Third Edition, September 2009; most recently modified version published online March 2022).
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n.1889