Article
Article
Osteostraci
Article By:
Denison, Robert H. Curator of Fossil Fishes, Field Museum of Natural History, Chicago, Illinois.
Last reviewed:January 2021
DOI:https://doi.org/10.1036/1097-8542.478800
An order of extinct jawless vertebrate fishes, also called Cephalaspida, known from the Middle Silurian to Upper Devonian of Europe, Asia, and North America. They were mostly small, about 2 in. (5 cm) to 2 ft (60 cm) in length. The head and part of the body were encased in a solid armor of bone, and the posterior part of the body and the tail were covered with thick scales. Some early forms lacked paired fins, although most possessed flaplike pectoral fins. One or two dorsal fins were present. Their depressed shape and the position of the eyes on the top of the head suggest that Osteostraci were bottom dwellers (Fig. 1). The underside of the throat region was covered by small plates and there was a small mouth in front.
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