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Agnathans, such as this lamprey, are distinguished by the lack of a jaw.


From Agnatha, from Ancient Greek ἀ- ‎(a-, without) + γνάθος ‎(gnáthos, jaw)


agnathan ‎(comparative more agnathan, superlative most agnathan)

  1. (zoology) Belonging or pertaining to the superclass Agnatha, the jawless vertebrates.
    • 2005, Tim Haines and Paul Chambers, The Complete Guide to Prehistoric Life, BBC Books, page 20:
      Haikouichthys is one of three species of jawless (or agnathan) fish to be found in the Early Cambrian period.


agnathan ‎(plural agnathans)

  1. (zoology) A member of the superclass Agnatha of jawless vertebrates.
    • 1956, D. R. Newth, "On the Neural Crest of the Lamprey Embryo", Journal of Embryology and Experimental Morphology, volume 4, page 358:
      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.
    • 1992, Peter J. Hanley et al., "Hagfish Humoral Defense Protein Exhibits Structural and Functional Homology with Mammalian Complement Components", Proceedings of the National Academy of Sciences, volume 89, page 7910:
      The hagfish is an agnathan, a modern representative of the earliest evolved group of vertebrates, the ostracoderms or jawless fishes, which arose prior to the ancient placoderms (3).




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