Daohugou, or, I love doing sequels

[David Marjanovic <david.marjanovic@gmx.at>]

The online full text of the *Volaticotherium* paper has a link to the 
following, to which I happen to have access:

Wang Xiaolin, Zhou Zhonghe, He Huaiyu, Jin Fan, Wang Yuanqing, Zhang Jiangyong, 
Wang Yuan, Xu Xing & Zhang Fucheng (2005): Stratigraphy and age of the Daohugou 
Bed in Ningcheng, Inner Mongolia, Chinese Science Bulletin 50(20), 2369 -- 2376

Abstract:
"Recent fieldwork has extended the distribution of the Daohugou Bed deposits 
from the Daohugou Village to its several neighboring areas. The fossil-bearing 
Daohugou deposits uncomformably overlie complex bedrocks, and comprise three 
major parts. The red shales in the lower part were misidentified as belonging 
to the Tuchengzi Formation. Field excavation has indicated that the shales of 
upper part of the bed are the major fossil-bearing horizon. Due to strong 
tectonic activities, sediments were often folded with the sequences inverted in 
the region. Some newly recognized contacts between the Daohugou Bed and the 
volcanic rocks showed that the ignimbrite of the Tiaojishan Formation (159--164 
Ma) underlies the Daohugou deposits, rather than overlying the latter as 
previously proposed. Thus, the age of the Daohugou deposits should be younger 
than the age of the ignimbrite, and thus it was incorrect to correlate the 
Daohugou Bed with the Middle Jurassic Jiulongshan Formation. Alt!
hough
 biostratigraphic studies based on conchostracans and insects support a Middle 
Jurassic-early Late Jurassic age for the Daohugou deposits, vertebrate fossils 
such as *Liaoxitriton*, *Jeholopterus* and feathered maniraptorans show much 
resemblance to those of the Yixian Formation. In other words, despite the 
absence of *Lycoptera*, a typical fish of the Jehol Biota, the Daohugou 
vertebrate assemblage is closer to that of the Early Cretaceous Jehol Biota 
than to any other biota. We propose that the Daohugou fossil assemblage 
probably represents the earliest evolutionary stage of the Jehol Biota based on 
both vertebrate biostratigraphy and the sedimentological and volcanic features 
which suggest the Daohugou deposit belongs to the same cycle of volcanism and 
sedimentation as the Yixian Formation of the Jehol Group."

Plenty of photos illustrate that:
- The layers are vertical in some places and describe amazing hairpin curves in 
others. Clearly, the Mongol-Okhotsk ocean was closed by a lot of force.
- The lower part of the Daohugou Bed contains gravel that is clearly derived 
from the -- underlying -- ignimbrite ( = Tiaojishan Fm). Thus, the Daohugou Bed 
is at most Late Jurassic in age.

The authors don't choose between Late Jurassic and Early Cretaceous, but note 
that the Daohugou Bed and the Yixian Fm are said to share some insect genera, 
in spite of similarities to other Asian insect faunas of diverse ages (such as 
that of the Late Jurassic Karabastau Fm, where *Batrachognathus* and *Sordes* 
are from).

No attempt at correlation to the Tuchengzi Fm (which does not exist in the 
area, contrary to the mentioned earlier misinterpretation by some of the 
authors) or the Dabeigou Fm (which doesn't exist there either) is mentioned. We 
are left with the whole range from the beginning of the Oxfordian to rather 
late in the Barremian, with only a slight tilt of the evidence toward the 
latter date.

The provenance of *Pterorhynchus* from the Daohugou Bed is confirmed, and 
*Scansoriopteryx* is also suspected to come from there (and to be a junior 
synonym of *Epidendrosaurus*).
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