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Ontogeny of the Carboniferous trilobite Paladin eichwaldi shunnerensis (King 1914)

Published online by Cambridge University Press:  03 November 2011

Euan N. K. Clarkson
Affiliation:
Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, Scotland, U.K.
Zhang Xi-guang
Affiliation:
Chengdu Institute of Geology and Mineral Resources, North Renmin Road, Chengdu, People's Republic of China.

Abstract

The Carboniferous trilobite Paladin eichwaldi shunnerensis (King 1914), at its type locality in northern England is exceptionally well-preserved, and shows all stages of growth from the degree 0 meraspis onwards. The post-protaspid ontogenyis described here with particular reference to the development of cuticular sculpture. On the dorsal surface of the smallest specimens a polygonal network of raised ridges (cell polygons) is apparent. With size increase, granules progressively appear amongst the polygons, which in turn change into large tubercles as the polygonal network fades. As the trilobite grows into an adult, the tubercles become relatively smaller, and pits, the openings of cuticular canals, appear amongst them. Marginal terrace lines become pronounced. On the hypostome, however, terrace lines become effaced centrally, while large pits develop. In the early meraspis the eyes are “schizochroal”, but the lenses rapidly become closely packed and contiguous and the eye is soon of “holochroal” type. The meraspid phase is passed through very rapidly. Whereas the earlymeraspis could not enroll, its pygidium could be bent down vertically, and this facility might have allowed the larva an escape reaction.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1991

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