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

Re: Steadman's review of Mesozoic Birds






From: "Tim Williams" <twilliams_alpha@hotmail.com>
Reply-To: twilliams_alpha@hotmail.com
To: dinosaur@usc.edu
Subject: Re: Steadman's review of Mesozoic Birds
Date: Fri, 30 Jan 2004 12:38:57 -0600

David Marjanovic wrote:

> >The debate over whether the magnetite contained
> >in the Martian meteorite is indeed biogenic
> >(and therefore indicative of past or present life on the Red Planet)

"Therefore"? We'd still have to rule out contamination -- colonization of
the meteorite by bacteria while it was lying around on the Antarctic ice.
IMHO that's quite likely what happened.

This is off-topic, so I'll be brief. (Then again, I started it.) Terrigenic contamination is unlikely, since the crystals are buried in a carbonaceous matrix that is itself of Martin composition. The debate has long since shifted to whether the crystals are of abiotic or biogenic origin.


It is the way Feduccia keeps up his
hypothesis. For example, it is plain obvious from all of his writings that
he has no good working knowledge about dinosaurs.

This is painfully true. Some of his statements about dinosaur anatomy or paleoecology date from the 1960's. Like David, a lot of the assertions made by Feduccia and Czerkas and Olson make me cringe. Many of the assertions have been contradicted over and over again, and in a multitude of papers (many of which have appeared in such obscure journals as Nature and Science and American Novitates).


Further, there are the internal inconsistences of his 'hypothesis'. For a long, long time Feduccia was convinced that the osteological similarities shared by dromaeosaurids and primitive birds were due to convergent evolution. Then dromaeosaurids turned up with honest-to-God feathers. Woops. Suddenly Feduccia was sidling up Czerkas' hypothesis: dromaeosaurids and birds were closely related after all, but neither evolve from dinosaurs.



Tim

_________________________________________________________________
High-speed users?be more efficient online with the new MSN Premium Internet Software. http://join.msn.com/?pgmarket=en-us&page=byoa/prem&ST=1




If I understand Feduccia's stance correctly, his actual contention is not that dromaeosaurs are related to birds but that forms like Microraptor are related to birds, and not related to dromaeosaurs. It makes little difference, one supposes, but nonetheless.

JGK

_________________________________________________________________
Scope out the new MSN Plus Internet Software ? optimizes dial-up to the max! http://join.msn.com/?pgmarket=en-us&page=byoa/plus&ST=1