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RATITES & ENANTIORNITHINES
Good to see we are still going strong on this issue of
ratite/palaeognath affinity and its application to the systematics of
Mesozoic non-ornithurines. Matt Troutman wrote...
> There is little fossil evidence to support the notion that ratites
> were roaming around in the mid Cretaceous.
My take at the moment is that ratites *are* monophyletic (see the
Pieters (1988)_Palaeotis weigelti_ paper for a good synthesis of all
the evidence: there is tons), and are primitive neornithines -
something most of those who advocate ratite monophyly agree with, but
which Mindell et al. (1997) seriously challange in their new
DNA-based tree (where the entire neornithine tree is turned on its
head - i.e. passerines are the most basal neornithines, galliforms
evolved later, anseriforms later still, and ratites are really
recently evolved). Now, if this is true (i.e. basal-ness of ratites),
it seems logical to argue that they evolved in the Late Cretaceous.
This is in agreement (I think) with Cooper and Miller's model of
'mass survival of birds across the KT boundary', but has no
supporting fossil evidence at the moment (the earliest ratite is
still _Diogenornis_ Alvarenga (1983) from the late Palaeocene).
Arguments for ratite polyphyly (e.g. Olson (1985) and Feduccia's _Age
of Birds_ - note that Feduccia (1996) has changed his mind about
gruiform affinities for ostriches), or that ratites are a
heterogenous assemblage of paedomorphic neognathans remain poorly
supported *and* fail to explain away lots of good evidence for ratite
monophyly. Furthermore, arguments used to support the very recent
evolution of certain flightless neognathans (e.g. Feduccia 1996) do
not prove that flightless groups cannot also be ancient (also,
Feduccia (1996) enjoys citing work that indicates youngness of
flightless taxa, but does not cite/is unaware of work that indicates
otherwise), especially when there is every evidence that they are.
> Really, all of the birds from the mid Cretaceous were
> enantiornithines, which are not related to any living birds
> according to EVERY SINGLE analysis cladistic or otherwise.
Well, stay tuned:) Matt's statement is not incorrect BUT no published
study codes ALL Mesozoic avian taxa in a data matrix (and by taxa, I
am talking about using genera as OTUs, not just higher-level taxa
like Neornithes). I have now seen a couple of (as yet) unpublished
data matrices that do this... the results are surprising!
"Charge the card - - - uh! Gambit's powers are gone too!"