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Science 22 August 1980:
Vol. 209. no. 4459, pp. 925 - 927
DOI: 10.1126/science.209.4459.925
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Articles

Geograpehic Variation and Episodic Evolution in an Ordovician Trilobite

JOHN L. CISNE 1, GEORGE O. CHANDLEE 2, BRUCE D. RABE 2, and JILL A. COHEN 3

1 Department of Geological Sciences and Division of Biological Sciences, Cornell University, Ithaca, New York 14853
2 Department of Geological Sciences, Cornell University
3 Department of Agronomy, Cornell University

A single lineage of the trilobite Flexicalymene shows two evolutionary "punctuated equilibria" within a 2-million-year, 1000-square-kilometer stratigraphic interval. The 2 x 105-year-long "punctuation" may represent parapatric speciation. Commonness of depth-related clines before, during and after this event suggests that short-term adjustment to local conditions was important in long-term evolution.

Submitted on January 4, 1980
Revised on May 15, 1980


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
ONTOGENY AND GEOGRAPHIC VARIATION OF A NEW SPECIES OF THE CORYNEXOCHINE TRILOBITE ZACANTHOPSIS (DYERAN, CAMBRIAN).
M. J. HOPKINS and M. WEBSTER (2009)
Journal of Paleontology 83, 524-547
   Abstract »    Full Text »    PDF »
Gradual or pulsed evolution: when should punctuational explanations be preferred?.
G. Hunt (2008)
Paleobiology 34, 360-377
   Abstract »    Full Text »    PDF »
Trilobite Tagmosis and Body Patterning from Morphological and Developmental Perspectives.
N. C. Hughes (2003)
Integr. Comp. Biol. 43, 185-206
   Abstract »    Full Text »    PDF »


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