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An extinct group of ostracoderms, or armored, jawless vertebrates; armor consisted of bone lacking cavities for bone cells.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a subclass of agnathous fossil vertebrates. Heterostraci were common during the Paleozoic era, from the Ordovician to the end of the Devonian. The shell was made of a varying number of schistoid plates of acellular bone, with a single (caudal) fin, lateral apophyses serving as supporting planes, and dorsal ridges, or spines, for the maintenance of equilibrium. The length of Heterostraci ranged approximately from several cm to 1 m. They inhabited both ocean and fresh waters, feeding on small organisms of the benthic and middle depths. Heterostraci are of great significance in the comparison of continental and marine deposits of the Middle Paleozoic.


Obruchev, D. V. “Vetv’ Agnatha: Bescheliustnye.” In Osnovy paleontologii: Bescheliustnye, ryby. Moscow, 1964.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
A new cyathaspid (Agnatha, Heterostraci) with an articulated oral cover from the Late Silurian of the Canadian Arctic.
The Boothiaspidinae, a new agnathan subfamily (Heterostraci, Cyathaspididae) from the Late Silurian and Early Devonian of the western United States and the Canadian Arctic.
A new ctenaspid (Agnatha, Heterostraci) from the Early Devonian of Nevada, with comments on taxonomy, paleobiology and paleobio-geography.
A new species of Ariaspis (Agnatha: Heterostraci) from the Late Silurian of the Canadian Arctic.
New species of the cyathaspidid Poraspis (Agnatha: Heterostraci) from the late Silurian and Early Devonian of Northwest Territories, Canada.
2004 A new species of Allocryptaspis (Heterostraci) from the Early Devonian, with comments on the structure of the oral area in cyathaspidids.
A new pteraspid (Agnatha, Heterostraci) from the Early Devonian Drake Bay Formation, Prince of Wales Island, Nunavut, Arctic Canada, and comments on environmental preferences of pteraspids.
Oredezhosteus, a new psammosteid genus (Heterostraci, Psammosteiformes) from the Lower Frasnian (Upper Devonian) of the Main Devonian Field.
O rode Psammosteus (Heterostraci) [About genus Psammosteus (Heterostraci)].
Notes on some early representatives of the Drepanaspida (Pteraspidomorphi, Heterostraci).
Phylogeny of the Pteraspidiforms (Heterostraci), Silurian-Devonian jawless vertebrates.