A critical reappraisal of the fossil record of the bilaterian phyla

@article{Budd2000ACR,
  title={A critical reappraisal of the fossil record of the bilaterian phyla},
  author={Graham E. Budd and S{\"o}ren Jensen},
  journal={Biological Reviews},
  year={2000},
  volume={75}
}
It has long been assumed that the extant bilaterian phyla generally have their origin in the Cambrian explosion, when they appear in an essentially modern form. Both these assumptions are questionable. A strict application of stem‐ and crown‐group concepts to phyla shows that although the branching points of many clades may have occurred in the Early Cambrian or before, the appearance of the modern body plans was in most cases later: very few bilaterian phyla sensu stricto have demonstrable… 

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