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Likelihood reinstates Archaeopteryx as a primitive bird.
Michael S Y Lee1, Trevor H Worthy
1South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia. mike.lee@samuseum.sa.gov.au
Biology Letters
|October 28, 2011
Summary
Phylogenetic analyses using likelihood methods restore Archaeopteryx as a basal bird, supporting a single origin of flight. Parsimony analysis weakly suggested a link with deinonychosaurs, indicating a hazy boundary between birds and theropods.
Area of Science:
- Paleontology
- Evolutionary Biology
- Phylogenetics
Background:
- The classification of Archaeopteryx, a pivotal fossil, has been debated.
- Recent phylogenetic analyses have challenged its traditional placement as a basal bird.
Purpose of the Study:
- To re-evaluate the phylogenetic position of Archaeopteryx using different analytical methods.
- To clarify the evolutionary origin of avian flight.
Main Methods:
- Phylogenetic analysis using both parsimony and maximum-likelihood/Bayesian methods.
- Analysis of morphological datasets to infer evolutionary relationships.
Main Results:
- Parsimony analysis weakly supported an Archaeopteryx-deinonychosaur clade.
- Maximum-likelihood and Bayesian methods robustly placed Archaeopteryx as a basal bird (bootstrap 73%, posterior probability 1).
- The Archaeopteryx-bird clade was supported by fewer, less homoplasious characters than the alternative clade.
Conclusions:
- Likelihood-based methods support Archaeopteryx as a basal bird, consistent with a single origin of powered flight.
- The boundary between advanced theropods and early birds remains complex.
- Both parsimony and likelihood methods are valuable for morphological phylogenetics.
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