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New information on the coaptative devices in the Ordovician trilobites Placoparia and Crozonaspis, and its significance for their classification and phylogeny

Published online by Cambridge University Press:  03 November 2011

J.-L. Henry
J.-L. Henry
Affiliation:
Laboratoire de Paléontologie et de Stratigraphie, Université de Rennes I, Campus de Beaulieu, 35042 Rennes cedex, France. (Centre National de la Recherche Scientifique, G.R.E.C.O. 130007 ct A. T. P. ‘Evolution’, projet E7).
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Abstract

Many Ordovician trilobites possess morphological structures on the cephalon, the pygidium and sometimes also on the thoracic segments, which interlock during enrolment. These coaptative devices, also known in living arthropods, are functional, inherited, and seem to remain stable at the species level. Significant evolutionary changes in coaptative devices occur throughout time within the genera Placoparia (Pliomeridae) and Crozonaspis (Dalmanitidae). New data are presented which have relevance for the details of the coaptative structures in Placoparia (Coplacoparia), and for the classification of the dalmanitid species morenensis and dujardini. In some species of Crozonaspis and in Placoparia (Coplacoparia), interlocking structures prevent the possibility of shearing between cephalon and post-cephalic exoskeleton.

Keywords

Armorican Massifenrolmentevolutionfunctional morphologyIberian PeninsulaOrdovicianCheirurinaPhacopina.
Type
Structure and function
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 76 , Issue 2-3: Fossil Anthropods as Living Animals , 1985 , pp. 319 - 324
Copyright
Copyright © Royal Society of Edinburgh 1985

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