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Fossils, molecules and embryos: new perspectives on the Cambrian explosionThe Cambrian explosion is named for the geologically sudden appearance of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals. Earlier indications of metazoans are found in the Neoproterozic; minute trails suggesting bilaterian activity date from about 600 million years ago. Larger and more elaborate fossil burrows appear near 543 million years ago, the beginning of the Cambrian Period. Evidence of metazoan activity in both trace and body fossils then increased during the 13 million years leading to the explosion. All living phyla may have originated by the end of the explosion. Molecular divergences among lineages leading to phyla record speciation events that have been earlier than the origins of the new body plans, which can arise many tens of millions of years after an initial branching. Various attempts to date those branchings by using molecular clocks have disagreed widely. While the timing of the evolution of the developmental systems of living metazoan body plans is still uncertain, the distribution of Hox and other developmental control genes among metazoans indicates that an extensive patterning system was in place prior to the Cambrian. However, it is likely that much genomic repatterning occurred during the Early Cambrian, involving both key control genes and regulators within their downstream cascades, as novel body plans evolved.
Document ID
20040142094
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Valentine, J. W.
(Department of Integrative Biology and Museum of Paleontology, University of California Berkeley, CA 94720, United States)
Jablonski, D.
Erwin, D. H.
Date Acquired
August 22, 2013
Publication Date
February 1, 1999
Publication Information
Publication: Development (Cambridge, England)
Volume: 126
Issue: 5
ISSN: 0950-1991
Subject Category
Geosciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
Review
Review, Academic
NASA Discipline Exobiology

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