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observations on the new Sapeornis specimens



Greetings,

The new Zhou & Zhang paper in Canadian Journal of Earth Sciences describes
two new specimens of _Sapeornis_, this time with skull material!

There are four conical, unserrated teeth in each premaxilla.  The number of
teeth in the maxilla is uncertain (at least one...), but no dentary teeth.
Both skulls are squished, so the precise shape is uncertain: the shape of
the mandible in the photos is much more like that of _Omnivoropteryx_ than
of _Archaeopteryx_, although the reconstruction gives the whole skull a very
Archie-look.

About 11 cervicals and 13 dorsal vertebrae, so more like your typical
non-ornithothoracine than like birdy birds.  Seven sacral vertebrae, and
perhaps 7 caudals anterior to the short pygostyle.  Gastralia are most
definitely present. No clear uncinate processes, nor any preserved sternum.

As in the type, the forelimbs are much longer than the hindlimbs (greater
proportionately than in any non-avialian theropod, _Archaeopteryx_,
_Shenzhouraptor_ (aka _Jeholornis), or _Confuciusornis_.  As mentioned in
the abstract (posted yesterday), there are only two phalanges (and no
ungual) on morphological digit III.  Lots of small gastroliths.  As in other
non-ornithurines (sensu Chiappe, not sensu Sereno), there is no triosseal
canal in the pectoral girdle.

Interesting critter, all told.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796