Re: semilunate carpal

["Tim Williams" <twilliams_alpha@hotmail.com>]

Dinogeorge wrote:

> ALL the most birdlike theropods appear in the fossil record AFTER
> Archaeopteryx and cannot possibly be its ancestors.

This may have more to do than the inadequacy of the Middle Jurassic 
terrestial fossil record than any *real* absence of pre-_Archaeopteryx_ 
maniraptorans.  There is tantalizing evidence of Jurassic maniraptorans 
(sensu Sereno, 1999 - oviraptorosaurs + deinonychosaurs + birds)... 
_Palaeopteryx_, _Nuthetes_ (though the paper has yet to come out, AFAIK), 
perhaps _Ozraptor_.  And that's just the skeletal-based taxa.  There's quite 
a number of teeth from various Jurassic sites (Guimarota and Morrison spring 
to mind, but there are others) which may pertain to maniraptorans.

> In BCF, this HAS to
> happen, because the birdlike theropods >descended from< the dino-birds. The
> fossil record, taken at face value, DIRECTLY CONTRADICTS ground-up/BADD.

Taken at "face value", yes.  But this is a pretty hefty caveat.  Isn't this 
the purpose of character analysis - to see if our "face-value" 
interpretations of the data hold up to scrutiny?

> The
> cladistics requires EVERY KNOWN theropod to have a substantial ghost 
> lineage
> to the point of its divergence from the dinosaur-to-birds lineage.

The ghost lineage separating _Archaeopteryx_ and basal dromaeosaurids (or 
basal deinonychosaurs) such as _Microraptor_ and _Sinornithosaurus_ may only 
be around 5-10 million years.  Is this really all that bad?  Compare (for 
example) the ghost lineage that links _Homo sapiens_ to chimpanzees (_Pan_).

> Not only is Archaeopteryx an advanced
> maniraptoran, it is also the EARLIEST ONE known, save perhaps for a few
> small, nondescript teeth of about the same age.

_Archaeopteryx_'s integument is highly derived, but its osteology is much 
less so (hence its "mosaic" morphology).  As I said in a previous response, 
_Archaeopteryx_'s skeleton is not all that different from that of many 
non-avian maniraptorans.  (Professor Ostrom, take a bow.)


Tim



---------------------------------------------------------------------

Timothy J. Williams

USDA-ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163




_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp