Joined: Jan. 2006
|The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals|
Douglas H. Erwin1,2,*, Marc Laflamme1, Sarah M. Tweedt1,3, Erik A. Sperling4, Davide Pisani5, Kevin J. Peterson6,*
1Department of Paleobiology, MRC-121, National Museum of Natural History, Post Office Box 37012, Washington, DC 20013Ė7012, USA.
2Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA.
3Behavior, Ecology, Evolution and Systematics, University of Maryland, College Park, MD 20742, USA.
4Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
5Department of Biology, The National University of Ireland, Maynooth, Kildare, Ireland.
6Department of Biology, Dartmouth College, Hanover, NH 03755, USA.
Diverse bilaterian clades emerged apparently within a few million years during the early Cambrian, and various environmental, developmental, and ecological causes have been proposed to explain this abrupt appearance. A compilation of the patterns of fossil and molecular diversification, comparative developmental data, and information on ecological feeding strategies indicate that the major animal clades diverged many tens of millions of years before their first appearance in the fossil record, demonstrating a macroevolutionary lag between the establishment of their developmental toolkits during the Cryogenian [(850 to 635 million years ago (Ma)], and the later ecological success of metazoans during the Ediacaran (635 to 541 Ma) and Cambrian (541 to 488 Ma) periods. We argue that this diversification involved new forms of developmental regulation, as well as innovations in networks of ecological interaction within the context of permissive environmental circumstances.