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Re: Tinamous: living dinosaurs
David Marjanovic <firstname.lastname@example.org> wrote:
> Both Hackett et al. (2008) and Harshman et al. (2008), using larger datasets
> than anyone else, independently found the tinamous to be nested deeply
> within the paleognaths. There are no ratites, there's just a bunch of
> paleognaths that lost flight several times independently.
Or the tinamous regained flight from a flightless ancestor. Harshman
et al. (2008) believe this scenario to be highly unlikely, but I
wouldn't disregard it completely - if the phylogeny is correct.
> Why do you use a classification as evidence in a discussion about
> phylogenetics? Classifications are (hopefully) _based on_ well-tested
> phylogenetic hypotheses, not the other way around.
It has to be said that although the 'Polyphyletic Ratites' hypothesis
has support from molecular data, it isn't supported by morphological
data. As Jason mentioned, the phylogenetic analysis of Dyke & Van
Tuinen (2004), which was based on osteological characters, recovered a
monophyletic ratite clade that excluded tinamous (Tinamidae).
Instead, Tinamidae, _Lithornis_ and _Palaeotis_ came up as successive
outgroups to the ratite clade within Palaeognathae. All too often we
are quick to regard a molecular analysis as inherently superior to a
morphological one. Harshman &c invoke convergence in postcranial
characters (associated with secondary loss of flight) as the
explanation for why osteology-based analyses produce a monophyletic
ratite group. They might be right; but I wouldn't assume that
phylogenetic analyses are so easily fooled. So I'm keeping an open
mind on ratite/tinamou relationships.