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Re: Moa-Tinamou Clade Found Within Ratites



On Wed, May 21st, 2014 at 11:15 AM, Tim Williams <tijawi@gmail.com> wrote:

> Then again, it may be that the most recent common ancestor of ratites
> and tinamous was a perfectly decent flier after all, and
> flightlessness (and near-flightlessnes in the tinamous) arose several
> times within the palaeognath clade.  Palaeognaths may have begun as
> rather small, volant birds with excellent flight abilities (unlike the
> tinamous).  Key to this is _Proapteryx_, the fossil kiwi (apterygid)
> from the early Miocene of New Zealand, which was smaller than extant
> kiwis and possibly volant (Worthy, 2013).  If basal apterygids were
> indeed volant, it improves the chances for kiwi ancestors to have
> arrived in NZ via overwater dispersal.

It may be the case that although palaeognaths were once all volant, they may 
have lacked certain 
adaptations that made it difficult to compete with neognaths. Their flight 
abilities may have been 
good enough in the absence of neognath competition, but it may not have cut the 
mustard where 
the two groups co-existed. That might explain why several palaeognath lineages 
lost flight 
independantly - once neognaths expanded into most environments on the planet, 
it just wasn't 
worth it for palaeognaths to retain their flight abilities when their new 
competition did it far better 
than they ever could. It may have been better to abandon that niche in favour 
of becoming 
flightless; a niche that neognaths may have also lacked the predisposing 
qualities to easily exploit. 
In the face of competition, niche partitioning is often the name of the game.

-- 
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Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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