- 1. adjectiveBelonging or pertaining to the superclass Agnatha, the jawless vertebrates.
Haikouichthys is one of three species of jawless (or agnathan) fish to be found in the Early Cambrian period.2. nounA member of the superclass Agnatha of jawless vertebrates.
Thus should the cranial neural crest in cyclostomes prove to be non-skeletogenous this might be a reflection either of its own primitiveness or of the different evolutionary origins and morphological status of the visceral skeleton in agnathans and gnathostomes.
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agnathan — n. 1. an eel shaped vertebrate without jaws or paired appendages; a member of the Agnatha. The group includes the cyclostomes and some extinct forms. Syn: jawless vertebrate, jawless fish [WordNet 1.5] … The Collaborative International Dictionary of English
agnathan — /ag neuh theuhn/, n. 1. any member of the vertebrate class Agnatha. adj. 2. agnathous. [AGNATH(A) + AN] * * * ▪ fish Introduction any member of the group of primitive, jawless fishes (fish) that includes the lampreys (lamprey) (order… … Universalium
agnathan — noun eel shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct forms • Syn: ↑jawless vertebrate, ↑jawless fish • Hypernyms: ↑aquatic vertebrate • Hyponyms: ↑ostracoderm, ↑ … Useful english dictionary
Agnatha — (Greek, no jaws ) is a paraphyletic [cite book|last=Purnell|first=M. A.|authorlink=|editor=Derek E. G. Briggs and Peter R. Crowther|year=2001|title=Palaeobiology II|publisher=Blackwell Publishing|location=Oxford|isbn=0 632 05149 3|page=p401; Note … Wikipedia
Heterostraci — Taxobox name = Heterostraci image caption = Drepanaspis gemuendenensis , accompanied by the placoderm Tiaraspis subtilis fossil range = Silurian Devonian |regnum = Animalia phylum = Chordata classis = Heterostraci subdivision ranks = Orders… … Wikipedia
Thelodonti — Temporal range: 453–359 Ma … Wikipedia
fish — fishless, adj. /fish/, n., pl. (esp. collectively) fish, (esp. referring to two or more kinds or species) fishes, v. n. 1. any of various cold blooded, aquatic vertebrates, having gills, commonly fins, and typically an elongated body covered with … Universalium
Fish — /fish/, n. Hamilton, 1808 93, U.S. statesman: secretary of state 1869 77. * * * I Any of more than 24,000 species of cold blooded vertebrates found worldwide in fresh and salt water. Living species range from the primitive lampreys and hagfishes… … Universalium
hormone — hormonal, hormonic /hawr mon ik, moh nik/, adj. /hawr mohn/, n. 1. Biochem. any of various internally secreted compounds, as insulin or thyroxine, formed in endocrine glands, that affect the functions of specifically receptive organs or tissues… … Universalium
Devonian Period — Interval of geologic time from 417 to 354 million years ago; it was the fourth period of the Paleozoic Era. During the Devonian, a giant continent was situated in the Southern Hemisphere (see Gondwana), and other landmasses were located in the… … Universalium