单词	hemichordate
释义	hemichordate /hɛmɪˈkɔːdeɪt / Zoology noun A marine invertebrate of the phylum Hemichordata; an acorn worm.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.... Unfortunately, a change in the genetic code of the mitochondrial genome in both enteropneusts and echinoderms strongly rejects chordate affinities of the hemichordates. 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. adjective Relating to or denoting hemichordates.Evidence for the hemichordate affinity of the extinct graptolites has been steadily amassing.... The hemichordate sequences always contained considerable support for both hypotheses. They lack two others, the notochord and post-anal tail, hence the name hemichordate.
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