Definition of hemichordate in English:



  • A marine invertebrate of the phylum Hemichordata; an acorn worm.

    • ‘Molecular phylogenies have suggested that hemichordates are in fact a sister lineage to the echinoderms.’
    • ‘Size comparisons between living and extinct hemichordate zooids are not conclusive evidence, however, as it is easy to imagine a small, hypothetical, zooid that possessed multiple tentaculated arms.’
    • ‘Unfortunately, a change in the genetic code of the mitochondrial genome in both enteropneusts and echinoderms strongly rejects chordate affinities of the hemichordates.’
    • ‘The molecular phylogeny does agree in one respect with the morphological one in that there are close similarities between the larvae of hemichordates (acorn worms and pterobranchs) and some echinoderms.’
    • ‘We chordates are deuterostomes, as are echinoderms, some marine worms called hemichordates, and the urochordates, or sea squirts.’


  • Relating to or denoting hemichordates.

    • ‘They lack two others, the notochord and post-anal tail, hence the name hemichordate.’
    • ‘Evidence for the hemichordate affinity of the extinct graptolites has been steadily amassing.’
    • ‘The hemichordate sequences always contained considerable support for both hypotheses.’
    • ‘There are two classes of hemichordate, the pterobranchs and the enteropneusts, which differ greatly in appearance and lifestyle.’
    • ‘Unfortunately there are no living fenestrate hemichordate species.’