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ostracoderm
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Cephalaspis, an armoured fishlike animal that belonged to the group of jawless vertebrates called ostracoderms. Drepanaspis Hemicyclaspis A branching diagram shows the evolutionary relationships among fossil and modern jawless fishes (Agnatha), with illustrations of Petromyzon, Myxine, Pharyngolepis, Pteraspis, Hemicyclaspis, and Drepanaspis along a timeline from the Ordovician period to the present.
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Related Topics:
lamprey
hagfish
heterostracan
Anaspida
Osteostraci
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Cephalaspis, an armoured fishlike animal that belonged to the group of jawless vertebrates called ostracoderms.
Cephalaspis, an armoured fishlike animal that belonged to the group of jawless vertebrates called ostracoderms.

ostracoderm

vertebrate group
Written by
Kevin Padian
Professor, Curator, University of California, Berkeley Museum of Paleontology. Editor of Encyclopedia of Dinosaurs.
Kevin Padian
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Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
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History
Drepanaspis
1 of 2
Drepanaspis
Hemicyclaspis
2 of 2
Hemicyclaspis

ostracoderm, an archaic and informal term for a member of the group of armoured, jawless, fishlike vertebrates that emerged during the early part of the Paleozoic Era (542–251 million years ago). Ostracoderms include both extinct groups, such as the heterostracans and osteostracans, and living forms, such as hagfishes and lampreys.

Kevin Padian