Book contents
- Frontmatter
- Contents
- Preface to the First Edition
- Preface to the Second Edition
- 1 Macroevolution: The Problem and the Field
- 2 Genealogy, Systematics, and Macroevolution
- 3 Genetics, Speciation, and Transspecific Evolution
- 4 Development and Evolution
- 5 The Constructional and Functional Aspects of Form
- 6 Patterns of Morphological Change in Fossil Lineages
- 7 Patterns of Diversity, Origination, and Extinction
- 8 A Cambrian Explosion?
- 9 Coda: Ten Theses
- Glossary of Macroevolution
- References
- Author Index
- Subject Index
8 - A Cambrian Explosion?
Published online by Cambridge University Press: 14 January 2010
- Frontmatter
- Contents
- Preface to the First Edition
- Preface to the Second Edition
- 1 Macroevolution: The Problem and the Field
- 2 Genealogy, Systematics, and Macroevolution
- 3 Genetics, Speciation, and Transspecific Evolution
- 4 Development and Evolution
- 5 The Constructional and Functional Aspects of Form
- 6 Patterns of Morphological Change in Fossil Lineages
- 7 Patterns of Diversity, Origination, and Extinction
- 8 A Cambrian Explosion?
- 9 Coda: Ten Theses
- Glossary of Macroevolution
- References
- Author Index
- Subject Index
Summary
All God's critters got a place in the choir
Some sing low, some sing higher,
Some sing out loud on the telephone wires,
And some just clap their hands, or paws, or anything they got now
– Bill Staines, 1979Introduction
No paleontological challenge rises higher above the landscape of evolutionary biology than the Cambrian Explosion of animal life. If the fossil record is to be taken literally, the Tommotian and Atdabanian stages of the Cambrian encompass the appearance of all but one of the modern bilaterian triploblastic animal phyla (Chen, Dzik, Edgecombe, Ramskøld, and Zhou 1995; Conway Morris 1989). The Manykaian stage presages this eruption with the appearance of a variety of spines and shells of more problematic groups (Bengtson 1977, 1992), and some shelly fossils are found in latest Precambrian rocks, even with evidence of predatory boreholes (Bengtson and Zhao 1992). The metazoan cornucopia pours out brachiopods, arthropods, echinoderms, priapulids, mollusks, onycophorans, and the rest – even chordates – all in rocks representing a breathtaking sprint of less than 10 million years (Bowring et al. 1993; Grotzinger et al. 1995). Only one readily preservable phylum, Bryozoa, still stubbornly refuses to be discovered in the Cambrian, but we can be sure that it is only a matter of time before it will be.
This is the wonderful story told by the rocks, but how sure can we be that what is “writ in stone” is all that reliable? Is it within the range of reason that all of the phyla could have arisen and diverged in so short a time?
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- Genetics, Paleontology, and Macroevolution , pp. 443 - 494Publisher: Cambridge University PressPrint publication year: 2001