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

[evelyn sobielski <koreke77@yahoo.de>]

--- David Marjanovic <david.marjanovic@gmx.at>
schrieb:

> > I went to one talk at GSA a few years ago, the
> whole point of which was
> > that the fieldwork attempted had been absolutely
> fruitless - no fossil
> > find whatsoever. Should we be taking more note of
> places where there
> > are "no dinosaurs here"?
> 
> Maybe. If there are more such places, maybe there's
> a pattern, and we might learn something from that.
> It's also far easier to cite something for the claim
> that there are "no dinosaurs here" than having to
> burrow through the entire literature and then write
> "the literature contains no mention of dinosaurs,
> but maybe we've overlooked some extra-obscure paper,
> or too undiagnostic specimens were not published" or
> the like.

True, but in such cases, I'd want to see a
comprehensive presentation on taphonomy and geology -
the site data, essentially, which would allow one to
see if some specific *kinds* of sites come up empty of
dinos.

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 (at least initially; Rahonavis I
*think* is too primitive in regards to its avian
parts), but given the gap above the Mirrison Fm.
(which IIRC still stands) and the uncertainty of
Archie's phylogenetic position I'm not 100% on this.
The Enantiornithes certainly were equipped for
transoceanic dispersal (as seen by Alexornis,
Yungavolucris, Lectavis, the avisaurids, probably also
Nanantius...) as were contemporary lineages that
diverged during c.130 mya Jurassic at latest and later
produced the Hesperornithes, Ichthyornithes etc. But
the exact dispersal pattern is still rather unclear;
the Late Cretaceous record of avians from NAm is what
one could possibly wish for (though most is in bits
and pieces) but before 100-90 mya it drops off rather
abruptly; it would be nice to be able to tell whether
this is due to sampling bias or to genuine absence
from a comprehensive sample.

Regards,

Eike


                
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