hemichordate

hemichordate

[hem-i-kawr-deyt] Zoology.
adjective
1.
belonging or pertaining to the chordates of the phylum Hemichordata, comprising small, widely distributed, marine animals, as the acorn worms.
noun
2.
a hemichordate animal, having a vertebratelike hollow nerve cord and an echinodermlike larval stage.

Origin:
1880–85; < Neo-Latin Hemichordata; see hemi-, chordate

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World English Dictionary
hemichordate (ˌhɛmɪˈkɔːˌdeɪt)
 
n
1.  any small wormlike marine animal of the subphylum Hemichordata (or Hemichorda), having numerous gill slits in the pharynx: phylum Chordata (chordates)
 
adj
2.  of, relating to, or belonging to the subphylum Hemichordata

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
hemichordate   (hěm'ĭ-kôr'dāt', -dĭt)  Pronunciation Key 
Any of various mostly small, wormlike marine invertebrates once thought to be chordates but now considered more closely related to echinoderms. They may constitute their own phylum, the Hemichordata. The bodies of hemichordates are divided into a feeding organ called a proboscis, a ringlike section called a collar, and a trunk. Hemichordates have a gut, circulatory system, and nervous system and are filter feeders. Acorn worms and graptolites are hemichordates.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

hemichordate

any of a group of wormlike marine invertebrates closely related to the chordates and sometimes considered to constitute a phylum, Hemichordata. The term Hemichordata-from the Greek hemi, meaning "half," and chorde, meaning "string," thus, "half-chordate"-was first proposed because the buccal diverticulum, a tubular outgrowth from the mouth cavity forward into the proboscis, or "snout," resembled a rudimentary notochord-the dorsal, or back-side, supporting axis of the more primitive vertebrates. This theory has since been rejected, however, because it has been determined that the diverticulum bears little resemblance in origin and function to the vertebrate notochord. Although the hemichordates are sometimes given phylum rank, some authorities place the group at various other taxonomic levels with the other so-called protochordates.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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