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Science 22 October 1999:
Vol. 286. no. 5440, pp. 760 - 763
DOI: 10.1126/science.286.5440.760
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Reports

Evolution of Complexity in Paleozoic Ammonoid Sutures

W. B. Saunders, 1* D. M. Work, 2 S. V. Nikolaeva 3

The septal sutures of 588 genera of Paleozoic ammonoids showed a 1600 percent increase in mean complexity over 140 million years. Within 475 ancestor/descendant pairs, descendants were more than twice as likely to be more complex than their ancestors. Twelve subclades (373 genera) averaged 34 percent increased complexity. These patterns are compatible with an active or driven system of long-term bias for increased complexity. Mass extinctions acted in opposition to this long-term trend, tending to eliminate more-complex forms and resetting the trend with each extinction event.

1 Department of Geology, Bryn Mawr College, Bryn Mawr, PA 19010, USA.
2 Cincinnati Museum Center, Geier Collections and Research Center, Cincinnati, OH 45202, USA.
3 Paleontological Research Institute, Russian Academy of Sciences, Profsoyuznaya 123, 117647 Moscow, Russia.
*   To whom correspondence should be addressed. E-mail: wsaunder{at}brynmawr.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Morphologic and taxonomic history of Paleozoic ammonoids in time and morphospace.
W. B. Saunders, E. Greenfest-Allen, D. M. Work, and S. V. Nikolaeva (2008)
Paleobiology 34, 128-154
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A generative bias towards average complexity in artificial cell lineages.
R. Lohaus, N. L Geard, J. Wiles, and R. B.R Azevedo (2007)
Proc R Soc B 274, 1741-1751
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New approaches to Fourier analysis of ammonoid sutures and other complex, open curves.
E. G. Allen (2006)
Paleobiology 32, 299-315
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Body size, extinction events, and the early Cenozoic record of veneroid bivalves: a new role for recoveries?.
R. Lockwood (2005)
Paleobiology 31, 578-590
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The evolution of complexity without natural selection, a possible large-scale trend of the fourth kind.
D. W. McShea (2005)
Paleobiology 31, 146-156
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Mass extinctions and macroevolution.
D. Jablonski (2005)
Paleobiology 31, 192-210
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Accounting for unequal variances in evolutionary trend mechanisms.
S. C. Wang (2005)
Paleobiology 31, 191-198
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The clymeniid dilemma: functional implications of the dorsal siphuncle in clymeniid ammonoids.
W. E. Gottobrio and W. B. Saunders (2005)
Paleobiology 31, 233-252
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Adaptive evolution in Paleozoic coiled cephalopods.
B. Kroger (2005)
Paleobiology 31, 253-268
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Morphological Disparity of Ammonoids and the Mark of Permian Mass Extinctions.
L. Villier and D. Korn (2004)
Science 306, 264-266
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The evolutionary history of shell geometry in Paleozoic ammonoids.
(2004)
Paleobiology 30, 19-43
Morphological pathways in the evolution of Early and Middle Devonian ammonoids.
(2003)
Paleobiology 29, 329-348
Finite-element analysis of simulated ammonoid septa (extinct Cephalopoda): septal and sutural complexities do not reduce strength.
(2002)
Paleobiology 28, 113-126
THE FUNCTION OF THE AMMONITE FLUTED SEPTAL MARGINS.
(2002)
Journal of Paleontology 76, 63-69
Lessons from the past: Evolutionary impacts of mass extinctions.
D. Jablonski (2001)
PNAS 98, 5393-5398
   Abstract »    Full Text »    PDF »
Lessons from the past: Biotic recoveries from mass extinctions.
D. H. Erwin (2001)
PNAS 98, 5399-5403
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Understanding the dynamics of trends within evolving lineages.
(2000)
Paleobiology 26, 319-329
Trends, tools, and terminology.
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Paleobiology 26, 330-333
Beyond competition.
(2000)
Paleobiology 26, 1-6


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