Early animal evolution: emerging views from comparative biology and geology.

  title={Early animal evolution: emerging views from comparative biology and geology.},
  author={Andrew H. Knoll and Sean B. Carroll},
  volume={284 5423},
The Cambrian appearance of fossils representing diverse phyla has long inspired hypotheses about possible genetic or environmental catalysts of early animal evolution. Only recently, however, have data begun to emerge that can resolve the sequence of genetic and morphological innovations, environmental events, and ecological interactions that collectively shaped Cambrian evolution. Assembly of the modern genetic tool kit for development and the initial divergence of major animal clades occurred… 
The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals
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.
The origin of animal body plans: a view from fossil evidence and the regulatory genome
It is assessed the emerging view that the early diversification of animals involved small organisms with diverse cell types, but largely lacking complex developmental patterning, which evolved independently in different bilaterian clades during the Cambrian Explosion.
Morphological and developmental macroevolution: a paleontological perspective.
Study of genomic differences among crown classes and orders whosetiming and mode of origin can be inferred from morphological data inthefossil record should throw further light on the timing and mode-of- origin of genomic disparities.
Recognizing and Interpreting the Fossils of Early Eukaryotes
Recognition of eukaryotic fossils in Proterozoic rocks is key to the integration of geological and comparative biological perspectives on protistan evolution.
Animal origins and the Tonian Earth system.
Compilations of the chromium isotope, micropaleontological, and organic biomarker records suggest that, as of now, the origin of animals was not obviously correlated to any environmental-ecological change in the Tonian Period, consistent with the idea that the evolution of animal multicellularity was primarily dictated by internal, developmental constraints.
Current advances in the phylogenetic reconstruction of metazoan evolution. A new paradigm for the Cambrian explosion?
  • G. Giribet
  • Biology
    Molecular phylogenetics and evolution
  • 2002
Evolution of animal body plans: the role of metazoan phylogeny at the interface between pattern and process
This work discusses how two recent important studies of animal body plan evolution, examining the evolution of the platyhelminth body plan and the evolutionary significance of indirect development and set‐aside cells, have actively incorporated two problematic aspects of the newly emerging molecular view of animal evolution: incomplete and unresolved phylogenies.


Early Metazoan Evolution: Reconciling Paleontology and Molecular Biology'
Reassessment of the evidence suggests that this pre-Ediacaran history was neither deep nor was represented by analogues of microscopic living metazoans, and the time-frame and search image need to be reset with this hypothesis in mind.
The Cambrian evolutionary ‘explosion’: decoupling cladogenesis from morphological disparity
Evidence is presented that 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.
Biostratigraphic and Geochronologic Constraints on Early Animal Evolution
Two distinct evolutionary pulses, represented by the Vendian Ediacaran fauna and Cambrian small shelly faunas, are generally thought to characterize the emergence of macroscopic animals at the end of
Fossils, molecules and embryos: new perspectives on the Cambrian explosion.
The distribution of Hox and other developmental control genes among metazoans indicates that an extensive patterning system was in place prior to the Cambrian, and it is likely that much genomic repatterning occurred during the Early Cambrian.
The early evolution of eukaryotes: a geological perspective.
Polecular phylogenies of eukaryotic organisms imply patterns of biological and environmental history that can be tested against the geological record, and Precambrian rocks show evidence of episodic increases in biological diversity and atmospheric oxygen concentrations.
Three-dimensional preservation of algae and animal embryos in a Neoproterozoic phosphorite
Embryos preserved in early cleavage stages indicate that the divergence of lineages leading to bilaterians may have occurred well before their macroscopic traces or body fossils appear in the geological record.
Monophyletic origins of the metazoa: an evolutionary link with fungi
A phylogenetic framework inferred from comparisons of small subunit ribosomal RNA sequences describes the evolutionary origin and early branching patterns of the kingdom Animalia and shows the animal lineage is monophyletic and includes choanoflagellates.
Molecular Evidence for Deep Precambrian Divergences Among Metazoan Phyla
It is suggested that invertebrates diverged from chordates about a billion years ago, about twice as long ago as the Cambrian, which suggests a prolonged radiation of animal phyla.
Origin of the metazoan phyla: molecular clocks confirm paleontological estimates.
This work has analyzed 18 protein-coding gene loci and estimated that protostomes (arthropods, annelids, and mollusks) diverged from deuterostomes about 670 million years ago, and chordates from echinoderms about 600 million years old, consistent with paleontological estimates.