[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: flights of fancy (or "I'm brave, but I'm chicken****")
>I think I've shown why I think it makes more sense--over and over and over.
>Others can accept my reasons or not. It really makes little difference to me
>at this point.
Do you mean to say that, having gone to all the trouble to develop and
present a hypothesis, you don't care if anyone buys it?
>Arm-tucking does not involve a particularly complex suite of characters. It
>is on the order of the loss of the outer digits and the elongation of the
>metapodials among cursorial animals. It could easily happen many times over,
>if it were that advantageous. And here again, I'm not saying "could not have
>evolved," I'm saying "unlikely to have evolved."
The same seems true of retractile claws. Remember that arm-tucking, like
retractility, also involves muscle and nerve adaptations - it isn't just a
piece of bone. Anyway, evolution is full of simple shifts that only
happened in certain groups.
>>This is circular reasoning. WHY are they flight-specific adaptations?
>>"Because birds have them" isn't enough.
>It's a damn good start. Big wings, trenchant claws, perching feet, flight
>feathers, lightweight pneumatic skeleton, large eyes--what's the big picture
>here? Ad hoc accumulation of random features, or a steady stream of features
>gradually acquired as improvements to an acronomic lifestyle?
A steady stream of features acquired as improvements to some sort of
lifestyle, clearly (except for "big wings" which non-volant maniraptors do
not demonstrably have). The argument is, which lifestyle - and all I am
saying is we can't be sure enough to found an entire phylogenetic
hypothesis. I think BCF would bother me a lot less if you were just a
little more uncertain about it...
>Skin impressions of large theropods exist, and they show no feathers. On the
>other hand, skin impressions of _Pelecanimimus_ do show some kind of
>featherlike structures(!), albeit neither contour feathers nor flight
I was not aware of this. Details? Anyway, Are there skin impressions of
any (other) non-avian maniraptor?
Ronald I. Orenstein Phone: (905) 820-7886 (home)
International Wildlife Coalition Fax/Modem: (905) 569-0116 (home)
Home: 1825 Shady Creek Court Messages: (416) 368-4661
Mississauga, Ontario, Canada L5L 3W2 Internet: firstname.lastname@example.org
Office: 130 Adelaide Street W., Suite 1940
Toronto, Ontario Canada M5H 3P5