Agnatha

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Agnatha

aquatic, jawless, fish-like vertebrates characterized by fewer than two pairs of limbs (fins). The group is often given the status of a subphylum to separate it from other vertebrates with jaws which are included in the subphylum Gnathostomata. The Agnatha includes lampreys, hagfish, and the fossil OSTRACODERMI.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
By imaging the internal structure of the skull using high-energy X-rays at the European Synchrotron (ESRF) in Grenoble, France, the authors show that the skull housed a brain with a short front end, very similar to that of a jawless vertebrate.
Between jawless vertebrates -- called agnathans -- and vertebrates with jaws-called gnathosomes-only three genes of the 12 genes the team looked at appeared to be used differently, Medeiros said.