Under Construction

Eriptychiidagroup is extinct

Philippe Janvier
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Containing group: Pteraspidomorphi

Introduction

The Eriptychiida, or eriptychiids, are a group of armored, fossil jawless vertebrates, which lived in the Middle Ordovician (about 450 million years ago) in North America. It is represented by two species, Eriptychius americanus and E. orvigi, known by only scales and armor fragments. A single specimen shows a partly articulated snout, whith traces of a calcified endoskeleton. Isolated branchial plates with a notch for the branchial opening suggest that their overall morphology was rather similar to that of the Astraspida. Eriptychius is found in association with the Astraspida.

Characteristics

Eriptychiids are characterized by:

The structure of the dentine of eriptychiids is in many respects closer to that of heterostracans that to that of astraspids. This is the only argument to place them as the closest relatives to heterostracans, among the Ordovician vertebrates. However, eriptychiids differ from all other pteraspidomorphs in having a massively calcified endoskeleton, pervaded by canals for blood vessels.

Discussion of Phylogenetic Relationships

The Eriptychiida are represented by a single, poorly known genus, Eriptychius, which superficially resembles Astraspis in having a tessellate headshield, but whose bone and dentine microstructure looks closer to that of heterostracans than to that of Astraspis. Eriptychiids occur in North America, usually in association with Astraspis.

References

Denison, R. H. (1967). Ordovician vertebrates from Western United States. Fieldiana: Geology, 16, 269-288.

Ørvig, T. (1958). Pycnaspis splendens, new genus, new species, a new ostracoderm from the Upper Ordovician of North America. Proceedings of the United States National Museum, 108, 1-23.

Ørvig, T. (1989). Histologic studies of ostracoderms, placoderms and fossil elasmobranchs. 6. Hard tissues of Ordovician vertebrates. Zoologica Scripta, 18, 427-446.

Title Illustrations
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Scientific Name Eriptychiida
Location Colorado
Comments The overall morphology of eriptychiids is still unknown, despite the abundance of their dermal bone fragments bearing large, oval tubercles, in the Ordovician of Colorado.
Reference from Ørvig, T. (1958). Pycnaspis splendens, new genus, new species, a new ostracoderm from the Upper Ordovician of North America. Proceedings of the United States National Museum, 108:1-23.
Body Part dermal bone fragment
Copyright © Smithsonian Institution Press
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Muséum National d'Histoire Naturelle Paris, France

Page: Tree of Life Eriptychiida. Authored by Philippe Janvier. The TEXT of this page is licensed under the Creative Commons Attribution License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

Citing this page:

Janvier, Philippe. 1997. Eriptychiida. Version 01 January 1997 (under construction). http://tolweb.org/Eriptychiida/16905/1997.01.01 in The Tree of Life Web Project, http://tolweb.org/

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