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28 - Tertiary

Published online by Cambridge University Press:  10 November 2010

Hans Hess
Affiliation:
Basel Natural History Museum, Switzerland
William I. Ausich
Affiliation:
Ohio State University
Carlton E. Brett
Affiliation:
University of Cincinnati
Michael J. Simms
Affiliation:
Ulster Museum, Belfast
Hans Hess
Affiliation:
Basel Natural History Museum
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Summary

THE POOR RECORD OF INTACT TERTIARY CRINOIDS

As a result of the distribution of sea and land during the Tertiary, which was similar to that of today, most marine sediments were deposited in shallow water close to present coastlines. Therefore, there are only a few chances to collect from deposits in which crinoids might be well preserved. The predominance among echinoderms of echinoids, and the extreme rarity of well-preserved crinoids in such sediments, is therefore no surprise. The presence of isocrinids (Metacrinus) in shallow-water sediments of Palaeocene to Oligocene age in New Zealand and the Antarctic Peninsula, as described later in this section, reveal the shift of these stalked crinoids to a deeper environment during the later Palaeogene (Stilwell et al. 1994). It must be assumed that, starting from a low at the Cretaceous–Tertiary boundary, the number of crinoid species has steadily increased during the Tertiary to arrive at the present diversity (see Fig. 3). The poor fossil record of Tertiary crinoids is, therefore, most probably due to non-preservation rather than to a lack of species. In fact, a remarkable number of crinoid remains have been found in the Danian (lowermost Palaeocene), and these include species of Cainocrinus, Calamocrinus, Isselicrinus, Nielsenicrinus and Bourgueticrinus and also comatulids (Rasmussen 1972).

Tertiary crinoids are commonly known only as stem fragments and cups; these remains belong to bourgueticrinids (Bourgueticrinus, Bathycrinus, Conocrinus, Democrinus) and isocrinids (Cainocrinus, Isselicrinus, Nielsenicrinus). In addition, dorsal cups (centrodorsals with radials) of comatulids are found. Complete specimens are very rare. Well-known examples are crowns of Isselicrinus subbasaltiformis from the Lower Eocene of Denmark and England.

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Chapter
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Fossil Crinoids , pp. 233 - 236
Publisher: Cambridge University Press
Print publication year: 1999

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