The Cambrian evolutionary ‘explosion’: decoupling cladogenesis from morphological disparity
- 14 January 1996
- journal article
- Published by Oxford University Press (OUP) in Biological Journal of the Linnean Society
- Vol. 57 (1), 13-33
- https://doi.org/10.1111/j.1095-8312.1996.tb01693.x
Abstract
The origin and differentiation of major clades is often assumed to have occurred in tandem with the ‘explosion’ of fossil evidence of diverse morphologies (‘disparity’) at the base of the Cambrian. Evidence is presented that this was not the case. Biogeographical and morphological differentiation among the earliest trilobites reveals incompleteness in the known early Cambrian record; similar evidence can be accrued for other major groups. Phylogenetic analysis proves the likelihood of ‘ghost’ lineages extending into the Precambrian. The important events in the generation of clades were earlier than the Cambrian ‘explosion’, at which time the groups become manifest in the fossil record. It is likely that the important phylogenetic changes happened in animals of small size; sister taxa of major groups are shown to be small animals. Decoupling cladogenesis from the Cambrian ‘explosion’ removes the necessity of invoking unknown evolutionary mechanisms at the base of the Phanerozoic. Genes controlling development may have played a role in generating new morphologies, through heterochrony for example, in the early differentiation of metazoan body plans.Keywords
This publication has 59 references indexed in Scilit:
- Burgess Shale-type fossils from a Lower Cambrian shallow-shelf sequence in northwestern CanadaNature, 1994
- Precambrian-Cambrian boundary global stratotype ratified and a new perspective of Cambrian timeGeology, 1994
- HOM/Hox Type Homeoboxes in the Chelicerate Limulus polyphemusMolecular Phylogenetics and Evolution, 1993
- Lower Cambrian acritarchs from northern Spain: the Precambrian-Cambrian boundary and biostratigraphic implicationsGeological Magazine, 1992
- The first molluscs ‐ small animalsBolletino di zoologia, 1992
- Meiofauna and the origins of the MetazoaZoological Journal of the Linnean Society, 1989
- Earliest known echinoderm — a new Ediacaran fossil from the Pound Subgroup of South AustraliaAlcheringa: An Australasian Journal of Palaeontology, 1987
- Early Land Animals in North America: Evidence from Devonian Age Arthropods from Gilboa, New YorkScience, 1984
- A new assessment of Rhyniella, the earliest known insect, from the Devonian of Rhynie, ScotlandNature, 1981
- Anaerobiosis, Meiofauna and Early Metazoan EvolutionZoologica Scripta, 1975