Re: An end to miracles (was Re: New alvarezsaurid)

[Jonathon Woolf <jwoolf@erinet.com>]

Dinogeorge wrote:

> In BCF, I argue that the aforementioned series of characters develops in
> theropods that have taken to (actually, retained from pre-dinosaurian
> archosaurs) an arboreal lifestyle.

Stupid question, maybe: if BCF is correct, then why are the oldest known 
theropods
(_Eoraptor_, _Herrerasaurus_) among the least birdlike theropods?

> Each character may then be understood as an
> incremental improvement to (or at least, in the context of) this lifestyle--it
> has a reason for existence that is related to flight (in the broad sense:
> parachuting, gliding, what have you; powered, flapping flight appeared much
> later, after many evolutionary "steps"). This is >not< to say that any
> character appeared because, sometime down the road, the animals were going to
> become powered, flapping fliers, but only that, whatever kind of flying the
> animals were doing was improved (somehow) by the appearance of the character.

Something here I don't understand.  There are a lot of arboreal animals that do
perfectly well without _any_ adaptations that could be even remotely interpreted
as leading toward flight.  So it's possible to be arboreal without being 
directed
onto a 'pre-flying' path by evolution.  Why, then, would these mini-dinos have
started that path?  What did it offer them that it does not offer, say, 
squirrels?

-- JSW