Re: _Archaeopteryx_

[jdharris@teal.csn.net (Jerry D. Harris)]

Rod -

> One fact seems to be regularly forgotten in these Archie discussions
> whenever they occur - he/she couldn't have 'flown' in the trus sense.  No
> keel!  That rather large, cartilagenous hunk of white stuff that all the
> white meat is attached to on your Christmas turkey (no sarcasm intended -
> sorry in that came across the wrong way!).  In the fossils of
> Archaeopteryx I've seen, I've never seen traces of the keel, which is an
> anchor for the large muscles required to power wing-driven flight.

        This isn't necessarily true.  The debate as to whether or not
_Archaeopteryx_ actually had a keel went on for a while; some, like de Beer
(1954) believed that the London specimen had at least a fragment of a
sternum; the newest specimen (thought by Wellnhofer to be a new species,
_Archaeopteryx bavarica_) does have a sternum (part of the reasoning behind
placing it into a new species).  It is, admittedly, small...but then again,
so are the sterna in such Early Cretaceous birds as _Sinornis_ and
_Iberomesornis_.  Some, like _Concornis_, have very large, keeled sterna!

        Back to _Archaeopteryx_:  prior to the discovery of the new
specimen, many had argued that _Archaeopteryx_ did indeed have a sternum,
but not one that ossified!  The huge keeled sternum to which you refer in
the Xmas turkey _is_ ossified -- that is, it is composed of bone, not
cartilage.  But in _Archaeopteryx_, a sternum could have been present, but
composed of cartilage.

        I have not yet seen the article in _Earth_ magazine, and thus
cannot speak to the specifics of the arguments presented there, but the
fact remains that the feathers of _Archaeopteryx_ (as detailed in the
Berlin specimen) most certainly _are_ asymmetrical -- see also Reitschel's
article "Feathers and the Wings of _Archaeopteryx_, and the Question of her
Flight Ability" in _The Beginnings of Birds_ for close-up photographs and
sketches of the feathers.  If _Archaeopteryx_ retains such charateristic
feathers for flight, then I have a difficult time believing that the animal
didn't fly!  Thus, I believe that the animal flew, although the small size
of the sternum (whether or not it was ossified) must have made it a
somewhat less graceful flier than modern birds.  The fact that the sternum
in only slightly younger birds (_Sinornis_, _Iberomesornis_, etc. on
through _Ambiortus_) grew in size rapidly points only to the quick
evolution of this trait to stabilize flight.

Jerry D. Harris
Denver Museum of Natural History
2001 Colorado Blvd.
Denver, CO  80205
(303) 370-6403

Internet:  jdharris@teal.csn.net
CompuServe:  73132,3372
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        "I repainted the picture Brown had painted for us.  A dying,
shrinking lake...these great...behemoths...dying..."
        "Well," she said, "all you tell me may be so...but I still can't
see why such creatures would have wanted to do it in the first place."
        "Do what, ma'am?"
        "Why, crawl away back under all that rock to die."

-- Roland T. Bird, _Bones for Barnum Brown_
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