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Facies preference predicts extinction risk in Ordovician graptolites

Roger A. Cooper and Peter M. Sadler
Facies preference predicts extinction risk in Ordovician graptolites
Paleobiology (May 2010) 36 (2): 167-187


The most abundant and diverse graptolite assemblages are found in offshore, deep-water black shales--the classical "graptolite facies" (deep-water or isograptid biofacies). The mean duration of Ordovician graptolite species confined to the deep-water facies (here referred to as "group 1" species) is 2.19 Myr, significantly shorter than the mean duration of species in the deep-water facies that are also known in sediments of the shallow-water shelf or platform ("group 2" species) -4.42 Myr, indicating a significantly higher extinction probability (p=<0.001). These figures are based on the precise age ranges of species derived from the time-calibrated composite sequence of 1446 Ordovician to early Devonian graptolites, built by the constrained optimization procedure (CONOP) from 256 measured sections worldwide, and exclude the effects of the Hirnantian mass extinction. The difference between groups cuts across families, morphological types, and pandemic/endemic distributions. An environmental influence is strongly suggested, and although both groups were planktonic, they were unlikely to have shared the same habitat in the water column. The new duration measurements therefore are interpreted as favoring a depth-stratification of graptolite habitats in the water column.

ISSN: 0094-8373
EISSN: 1938-5331
Serial Title: Paleobiology
Serial Volume: 36
Serial Issue: 2
Title: Facies preference predicts extinction risk in Ordovician graptolites
Affiliation: GNS Science, Lower Hutt, New Zealand
Pages: 167-187
Published: 201005
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 75
Accession Number: 2010-039593
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes 3 appendices
Illustration Description: illus. incl. 5 tables
Secondary Affiliation: University of California Riverside, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201022
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