Re: Mesozoic Snow

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

Tom wrote:

> Pedopenna is definitely feathered, and *might* be from the Middle Jurassic.
> (Indeed, most of the Chinese paleos and geologists I
> have spoken to are very certain about that date).

     Well, they're all wrong.  OK, I can't say that with 100% certainty, 
but this paper:

He, H. Y., Wang, X. L., Zhou, Z. H., Zhu, R. X., Jin, F., Wang, F., Ding, 
X., and Boven, A. 2004. 40Ar/39Ar dating of ignimbrite from Inner Mongolia, 
northeastern China, indicates a post-Middle Jurassic age for the overlying 
Daohugou Bed. Geophysical Research Letters 31:L20609.

...provides a date from a bed UNDER the Daohugou Formation as Oxfordian 
(early Late Jurassic), which means that the Daohugou is Late Jurassic or 
younger. They don't discuss the nature of the contact between the ignimbrite 
and the Daohugou (i.e., conformable or unconformable), so that in an of 
itself doesn't mean anything. It is interesting that none of the classic 
Jehol Biota taxa have yet been recovered from the Daohugou (or, at least, 
not reported in any paper I have access to), but neither does the Dabeigou 
Formation (source of _Protopteryx_), and the latter is considered Early 
Cretaceous by most workers.  Not that the Daohugou and Dabeigou are 
necessarily correlates -- just interesting that pre-Jehol formations _have_ 
produced feathered animals.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
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