The nature of cladistics (birds and dinosaurs)
Tpape at ZMUC.KU.DK
Sat Nov 20 11:50:17 CST 2004
- Velociraptor and Corvus share these complex feathers,
- similar eggshell microstructure, and lots of other synapomorphies
- (which are lacking in tyrannosaurs, non-coelurosaur saurischians,
- and ornithischians).
I think Ken has provided an excellent example of why cladistic grouping according to shared derived features (i.e., into monophyletic groups), has a superior information content and more explanatory power than the grouping based on symplesiomorphies, which leads to paraphyletic groups. Accomodating Velociraptor in a group with Corvus and all the other taxa sharing complex feathers conveys more information about evolutionary change than accomodating Velociraptor in a group together with tyrannosaurs, non-coelurosaur saurischians, and ornithischians (but excluding Corvus). Whether we call Velociraptor a bird, a reptile-like bird, a bird-like reptile or a reptile is not an issue. The issue is what information we want to convey and how we do that most efficiently. Monophyletic groups point to character state transformation and as such to evolutionary events.
Thomas Pape, Zoological Museum, University of Copenhagen
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