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Calibrating the Ordovician Radiation of marine life: implications for Phanerozoic diversity trendsIt has long been suspected that trends in global marine biodiversity calibrated for the Phanerozoic may be affected by sampling problems. However, this possibility has not been evaluated definitively, and raw diversity trends are generally accepted at face value in macroevolutionary investigations. Here, we analyze a global-scale sample of fossil occurrences that allows us to determine directly the effects of sample size on the calibration of what is generally thought to be among the most significant global biodiversity increases in the history of life: the Ordovician Radiation. Utilizing a composite database that includes trilobites, brachiopods, and three classes of molluscs, we conduct rarefaction analyses to demonstrate that the diversification trajectory for the Radiation was considerably different than suggested by raw diversity time-series. Our analyses suggest that a substantial portion of the increase recognized in raw diversity depictions for the last three Ordovician epochs (the Llandeilian, Caradocian, and Ashgillian) is a consequence of increased sample size of the preserved and catalogued fossil record. We also use biometric data for a global sample of Ordovician trilobites, along with methods of measuring morphological diversity that are not biased by sample size, to show that morphological diversification in this major clade had leveled off by the Llanvirnian. The discordance between raw diversity depictions and more robust taxonomic and morphological diversity metrics suggests that sampling effects may strongly influence our perception of biodiversity trends throughout the Phanerozoic.
Document ID
20040089776
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Miller, A. I.
(University of Cincinnati Ohio 45221-0013, United States)
Foote, M.
Date Acquired
August 21, 2013
Publication Date
March 1, 1996
Publication Information
Publication: Paleobiology
Volume: 22
Issue: 2
ISSN: 0094-8373
Subject Category
Geosciences (General)
Funding Number(s)
CONTRACT_GRANT: DEB-9496348
CONTRACT_GRANT: DEB-9207577
CONTRACT_GRANT: NAGW-3307
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Exobiology

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