RE: Journal of Negative Results -- Ecology & Evolutionary Biology

["Jerry D. Harris" <jharris@dixie.edu>]

> For example, I'd love to have a list of NAm Early
> Cretaceous sites where *no* avians have been found.
> Archie and paleobiogeography indicate that
> theroretically there might have been numerous avians
> by 120 mya, but as the NAm Mesozoic fossil record is
> fairly well worked over, I find it rather doubtful
> that not much has turned up. For example, the Morrison
> Formation is extensive, well worked, and roughly
> contemporary with Solnhofen, and habitat was roughly
> similar (though inland rather than coastal as
> Solnhofen). The lack of anything avian from the
> Morrison Fm. lets me conclude that "ornithization" -
> accumulation of sufficient "bird" features by one or
> more theropod lineage(s) to allow powered flight -
> took place in Eurasia.

    Ah, yes...the old "absence of evidence is evidence of absence" 
fallacy -- not that I for a moment think (based on your past posts) that 
you've done this intentionally.  In my experience, a good paleontological 
adage ought to be "Never underestimate the Morrison Formation."  Everyone 
ALWAYS thinks it's "well worked," meaning that new discoveries are 
invariably the same ol', same ol' taxa.  While it is true that Morrison 
workers keep finding new specimens of known taxa, the unit also continues to 
produce surprises...new sauropods (e.g., _Suuwassea_, others being described 
at present), stegosaurs (_Hesperosaurus_ and probably others being worked on 
presently), ankylosaurs (unknown before the last decade), little theropods 
(e.g., _Tanycolagreus_, Scott Hartman's troodontid), really decent pterosaur 
material (e.g., _Harpactognathus_), and, perhaps most interestingly, mammals 
(e.g., _Fruitafossor_).  As T. Mike mentioned, there are some potentially 
avian (avialan, if you prefer) bones known, some of which were initially 
described as avian (e.g., stuff from the Dry Mesa quarry) that is, at the 
very least, maniraptoran, probably eumaniraptoran.  The presence of a 
troodontid indicates that paravians were most certainly milling about 
Morrison landscapes, and it wouldn't surprise me a bit if a true 
archaeopterygian or something of similar "grade" showed up in the Morrison 
one day.  (I hope I'm the one to find it, but there are people doing a 
heckuva lot more field work in the Morrison than me, so...)  In short, the 
Morrison is far, far from exhausted, and in no way can the absence of avians 
in it thus far be construed as evidence that they weren't there!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

"Trying to estimate the divergence times
of fungal, algal or prokaryotic groups on
the basis of a partial reptilian fossil and
protein sequences from mice and humans
is like trying to decipher Demotic Egyptian with
the help of an odometer and the Oxford
English Dictionary."
              -- D. Graur & W. Martin (_Trends
                  in Genetics_ 20[2], 2004)