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Early animal evolution: a morphologist's view
1The Natural History Museum of Denmark, University of Copenhagen, Zoological Museum, Universitetsparken 15, DK-2100 Copenhagen, Denmark.
Royal Society Open Science
|August 17, 2019
Summary
Morphological analysis strongly supports the Porifera-first hypothesis for early animal evolution, suggesting sponges are the sister group to all other metazoans. This contrasts with the Ctenophora-first hypothesis, which implies significant character losses.
Area of Science:
- Zoology
- Evolutionary Biology
- Phylogenetics
Background:
- Recent phylogenomic studies debate early metazoan radiation hypotheses.
- Key hypotheses include 'Porifera-first' and 'Ctenophora-first'.
Purpose of the Study:
- To analyze morphological characters to resolve the controversy in early metazoan evolution.
- To evaluate the implications of both 'Porifera-first' and 'Ctenophora-first' hypotheses.
Main Methods:
- Comparative morphological analysis of key characters.
- Evaluation of character homoplasies and losses under different phylogenetic scenarios.
Main Results:
- The 'Porifera-first' hypothesis implies no major character losses or homoplasies.
- The 'Ctenophora-first' hypothesis suggests independent evolution or loss of complex traits like digestive systems.
- Morphological evidence does not support significant adaptive advantages for losses implied by the 'Ctenophora-first' hypothesis.
Conclusions:
- Morphological data provide strong support for the 'Porifera-first' hypothesis.
- The 'Ctenophora-first' hypothesis requires substantial, unparsimonious character evolution or loss.
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