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Agnatha ( Greek , "no jaws") is a Super-class of jawless fish in the phylum Chordata, Sub-Phylum Vertebrata. There are about 60 modern species divided into Lampreys and Hagfish. In addition to the absence of jaws, Agnatha are characterised by absence of paired fins; presence of a notochord both in larvae and adults; seven or more paired gill pouches. The branchial arches supporting the gill pouches lie close to the body surface. There is a light sensitive pineal eye . There is no identifiable stomach. Fertilization is external. The Agnatha are ectothermic, and the heart contains 2 chambers. Individual hagfish are hemaphrodorphic , with both ovaries and testes, but the female gonads are not functional. Lampreys are bisexual. Hagfish do not have a larval stage whereas Lampreys have a long larval phase.

Lampreys are reasonably successful parasitic predators. They attach themselves to other marine animals and abrade a hole through the skin with their rasp like tongue in order to attack the underlying tissues. Modern lampreys always spawn in fresh water although many spend at least part of their life in the sea. Hagfish are marine and alternate between functioning as scavangers, parasites, and as active predators consuming marine wormA worm is any of numerous relatively small elongated soft-bodied invertebrate animals. The most famous is the earthworm, a member of phylum Annelida, but there are hundreds of thousands of different species that live in a wide variety of habitats other ths.

Although a minor element of modern marine faunaFauna is a collective term for animal life. The corresponding term for plants is flora. Technically, the proper term for fauna plus flora is biota but fauna is often used instead. In zoology and paleontology the term is often used to refer to the typical, Agnatha were prominent among the early fish in the early Paleozoic. Two types of an Early CambrianThe Cambrian is a major division of the geologic timescale that begins about 542 million years before the present (BP) at the end of the Proterozoic eon and ended about 490 million years BP with the beginning of the Ordovician period. It is the first peri animal with apparent fins, vertebratePetromyzontidae ( lampreys) Placodermi extinct Chondrichthyes (cartilaginous fish) Acanthodii extinct Actinopterygii (ray-finned fish) Actinistia ( coelacanths) Dipnoi ( lungfish) Amphibia ( amphibians) Reptilia ( reptiles) Aves ( birds) Mammalia ( mammal musculature, and with gills are known from the early CambrianThe Cambrian is a major division of the geologic timescale that begins about 542 million years before the present (BP) at the end of the Proterozoic eon and ended about 490 million years BP with the beginning of the Ordovician period. It is the first peri Maotianshan shalesThe Maotianshan shale is an early Cambrian rock formation exposed in the Yunnan Province of China in the villages of Ercaicun and Chengjiang near the city of Kunming. These shales appear very early in the Cambrian sequence in China. They were discovered a of China - Haikouichthys and Myllokunmingia. They have been tentatively assigned to Agnatha by Janvier. A third possible agnathid from the same region is Haikouella. A possible agnathid that has not been formally described was reported by Simonetti from the Middle Cambrian Burgess Shale of British Columbia. Agnathids were well established by the late Ordovician and are found in the Silurian as well. The Ostracoderms subclass included some of the largest fossil vertebrates that ever lived. Agnathids declined in the Devonian and never recovered.

Modern agnathids generally have cartilaginous skeletons. Ordovician and Silurian agnathids were armored with heavy bony plates. Neither modern nor suspected Cambrian agnathids were/are armored.