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Priscomyzon
''Priscomyzon riniensis'' is an extinct lamprey that lived some 360 million years ago during the Famennian (Late Devonian) in a marine or estuarine environment South Africa. This small agnathan is anatomically similar to the Mazon Creek lampreys, but is some 35 million years older. Its key developments included the first known large oral disc, circumoral teeth and a branchial basket.
==Context==
Though common and diverse during the Silurian and Devonian, jawless fish are today represented only by lampreys and hagfish, both groups being quite specialized. Lampreys have seven gill pouches (whereas jawed fish have only five), no paired fins, and a rudimentary skeleton of cartilage. They also have a sucker disc of cartilage surrounded by a soft lip and a central small mouth set about with simple hooked teeth. They attach to the bodies of other vertebrates by suction, securing their grip with the hooked teeth, after which a rasped tongue scrapes a hole providing access to the host's softer tissues.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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