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Trilobite abnormalities

Published online by Cambridge University Press:  03 November 2011

Alan W. Owen
Alan W. Owen
Affiliation:
Department of Geology, The University, Dundee DD1 4HN, Scotland.
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Abstract

There is abundant evidence of injury, teratology and pathological conditions in trilobites although it is commonly difficult to distinguish between their morphological results. Many injuries were probably sustained during moulting, with spines, bilamellar fringes and narrow gaps between dorsal exoskeleton and doublure being most vulnerable. Some injuries were the result of predaceous attack and provide important clues to the trophic structure of Palaeozoic communities. Many injuries show evidence of repair. Some supposedly teratological conditions, most notably the number of paradoxidid thoracic segments, are so common that they must be considered part of normal variation. Others represent genetic mutation or ontogenetic malfunction, the latter possibly externally induced. Undoubted pathological conditions are restricted to swellings and borings presumably caused by parasitic infestation.

Abnormalities affecting lateral areas are more common than those involving the rachis and glabella and this probably reflects both greater mortality when the axial region is involved, and greater vulnerability of peripheral regions to predaceous and moulting damage. The first explanation also accounts for the rarity of cephalic abnormalities compared to those of the pygidium.

Keywords

healinginjurymoultingparasitespathologypredationteratology

Information

Type
Life and environment of fossil forms
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 76 , Issue 2-3: Fossil Anthropods as Living Animals , 1985 , pp. 255 - 272
Copyright
Copyright © Royal Society of Edinburgh 1985

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