[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Ancestors and descendants (story for Nick)

Jeffrey Martz wrote:

Is the weight-bearing front foot of a Diplodocus any less
different from the clawed theropod hand then the flying forelimb of a bird?
Birds might be impressively diverse and specialized fliers, but I would
hesistate to say they are really any more derived from the little meat
eating runner design then sauropods or Ornithischians.

All spot on! However, the implicit and overriding theme of the Kinman-ian scheme is PROGRESS! Because of their warm-blooded-ness and the profound anatomical innovations (in the musculature and skeleton) that birds underwent in order to achieve powered flight, the birds deserve their own "Class" among the vertebrates. We see birds soaring over our heads, but not (fingers crossed) _Diplodocus_. You and I may believe that birds are just flying theropods. To the Kinman way of thinking, birds have moved UP the evolutionary ladder and have graduated to a Class of their own. I can't imagine a dissection of _Deinonychus_ would reveal all that much different to _Archaeopteryx_, but the latter makes the cut into Class Aves, _Deinonychus_ doesn't.

Mammals also get their own Class because, like birds, they are also blessed with warm-blooded-ness. The classes Aves and Mammals were principally formulated for this reason.

By the same peculiar reasoning, the vast array of basal archosauromorphs and basal archosaurs all get dumped into the "Thecodontiformes" - a polyglot wastebasket including rhynchosaurs, champsosaurs, poposaurs, phytosaurs, ornithosuchids, etc etc.

The Kinman-ian system doesn't make an iota of sense to me. As I said, it combines the worst aspects of hierarchial and cladistic methods.


Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com