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A comparative study of diversification events: the early Paleozoic versus the MesozoicWe compare two major long-term diversifications of marine animal families that began during periods of low diversity but produced strikingly different numbers of phyla, classes, and orders. The first is the early-Paleozoic diversification (late Vendian-Ordovician; 182 MY duration) and the other the Mesozoic phase of the post-Paleozoic diversification (183 MY duration). The earlier diversification was associated with a great burst of morphological invention producing many phyla, classes, and orders and displaying high per taxon rates of family origination. The later diversification lacked novel morphologies recognized as phyla and classes, produced fewer orders, and displayed lower per taxon rates of family appearances. The chief difference between the diversifications appears to be that the earlier one proceeded from relatively narrow portions of adaptive space, whereas the latter proceeded from species widely scattered among adaptive zones and representing a variety of body plans. This difference is believed to explain the major differences in the products of these great radiations. Our data support those models that hold that evolutionary opportunity is a major factor in the outcome of evolutionary processes.
Document ID
20040120343
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Erwin, D. H.
(Michigan State University East Lansing 48824, United States)
Valentine, J. W.
Sepkoski, J. J. Jr
Sepkoski JJ, J. r.
Date Acquired
August 22, 2013
Publication Date
January 1, 1987
Publication Information
Publication: Evolution; international journal of organic evolution
Volume: 41
Issue: 6
ISSN: 0014-3820
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: EAR84-17011
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Exobiology
Non-NASA Center

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