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Re: Birds, dinosaurs, and digit 1



In a message dated 97-10-24 20:41:11 EDT, WOlewiler@aol.com writes:

<< Reactions:  Mark Norell, American Museum of Natural History, NYC -- "There
is
 a discrepancy between what the embryology tells us and what the fossils tell
 us. No one feature, such as a thumb, can sway things one way or another.
 Storrs Olson, Smithsonian -- This "is the end of it as far as I am
concerned.
 There is no way that birds and dinosaurs could be directly related."
 
 How does this research relate to Birds Came First? >>

The simplest way to reconcile this result, if it is in fact correct and not a
misinterpretation (as some think has happened), is to note that there were
many theropods with four-fingered hands (ceratosaurians) from which modern
birds might have descended, eliminating digit I and retaining digits II-IV.
But the correspondence of phalangial counts >and shapes< in maniraptoran
dinosaurs to those in _Archaeopteryx_, not to mention the remainder of the
skeletal anatomy, pretty much nails down the close relationship between those
two forms and strongly suggests that avian wing digits are I-III. If II-IV in
modern birds is correct, then _Archaeopteryx_, despite its feathers, is only
a distant relative of modern birds and not close to modern-bird ancestry.
That is, there would have to be at least two distinctly different avian wing
types in the Mesozoic: those with digits II-IV and those with digits I-III.
Maybe this difference also correlates with ornithurans (II-IV) and
enantiornithans (I-III)? Maybe _Protoavis_ (more modern-looking than
_Archaeopteryx_, according to Chatterjee) represents a primitive ornithuran,
whereas the commonest Cretaceous birds were all enantiornithan? Lots of
different ways not to throw the baby out with the bath water.