Gansus: AAAS presentation and paper

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

Greetings,

A brief report on both the talk last night and on the data in the paper.

Jerry Harris, Matt Lamanna, and Hai-lu You were the presenters for the first 
ever "Meet the Science Authors" event. AAAS is starting
this new series--a VERY good idea, in my opinion--of outreach to the general 
public by hosting informal receptions, non-technical
presentations, and Q&A sessions for new papers of broad interest. I hope they 
continue to do this. As this was an "experiment" the
word hadn't gotten around that well (not too many people from the Smithsonian 
were there, for example), but will hopefully improve
with the next few iterations. A fair number of youngsters were present, too.

Peter Dodson was in the audience, but did not present. The three guys in the 
"hot seats" did well at explaining the situation of
Mesozoic bird studies over the last 15 years or so; the nature of _Gansus_ 
ornithiurine anatomy; and the fossil site and nearby
locality itself. About the latter: the Changma site of the Xiagou Fm. 
(Aptian/Albian boundary) has extremely well laminated
lacustrine deposits. They are oriented nearly vertically due to tectonic 
activity of the nearby encroaching Tibetan plateau... Also,
the town nearby was so nicely green and rural that they referred to it as "The 
Shire".

No non-avian dinos yet reported from this unit, but plenty of plants, fish, 
insects, crustaceans, isolated feathers, and many many
birds. (A lot of these are still in preparation, so hopefully more information 
is forthcoming about Gansus and about other
Aptian/Albian birds). I asked them about the presence of choristoderes, and 
they said they haven't found any yet: odd, given that
the Yixian and Jiufotang are lousy with them. But the outcrop is big, so 
they're still looking.

As for the critter itself: _Gansus_ is pigeon sized. The skull is not yet 
known, so the restoration is an amalgam of _Ichthyornis_
and hesperornithiform features. Soft tissue preservation shows webbed feet. 
Most features are very neornithine/carinate-like, but
the presacrals are non-heterocoelous. Some wing feathers and semiplumes are 
preserved.

The humerus and coracoids are apneumatic. The size and shape of the cnemial 
crest, and the shape and proportions of the digits, are
consistent with a foot-propelled diver.

Their phylogenetic analysis places it intermediate between hesperornithiforms 
and Carinatae (_Ichthyornis_ + Neornithes).
Consequently, it is the oldest member of Ornithurae based on their phylogeny.

Cool stuff.

                Thomas R. Holtz, Jr.
        Senior Lecturer, Vertebrate Paleontology
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
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Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
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