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RE: Olfactory Lobes & Large Yixian Theropods (was Re: New here, General Qs)



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Nick Gardner
>>
_Tyrannosaurus bataar_ is described as having large
> olfactory lobes
> (Maleev, 1965).  _Giganotosaurus carolinii_ appears to have
> moderately sized
> olfactory lobes (Coria & Currie, 2002).

Unfortunately, the exact size of the olfactory bulbs in either of these
forms is less well-constrained than in _T. rex_ (for which the volume is
well-established thanks to Brochu's CAT scans).  For example, in the case of
_Giganotosaurus_, one can see from Fig. 9 in Coria & Currie's paper that the
anterior and anteroventral extent of the bulbs are not fully known.

Endocasts of an _Allosaurus_ brain have been described, with smaller bulbs
than _Gig._ or _Tyrannosaurus_, but it is an absolutely smaller sized
animal.

>
> Sadly, there are not yet any large theropods recovered from the Yixian
> Formation.  Come to think of it, off hand, I can't think of any large
> vertebrates from the Yixian.  If there are, could someone please
> list them
> with length and mass estimates?
>
The ornithopod Jinzhousaurus was about 7 m long.  Mass estimates... good
question.  Sound's _Gryposaurus_ size, so maybe 2 tonnes?

Undescribed sauropod material from the lower Yixian (again, possibly the
fluvial rather than lacustrine beds) are reported in:

Wang, X.-L. et al. Stratigraphic sequence and vertebrate-bearing beds of the
lower part of the Yixian Formation in Sihetun and neighbouring area, western
Liaoning, China. Vert. PalAsiat. 36, 81?101(1998). (cited in Zhou et al.'s
recent review in Nature).

                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