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RE: Dinos galore /ZPAL MgD I/4






> > Describes a WONDERFUL new skull of Tarbosaurus bataar ZPAL
> MgD-I/4, giving
> a
> > good comprehensive cranial osteology of this species.
>
>   Isn't the specimen a subadult? I think the length of the ZPAL MgD I/4
> skull is only 1.05m, smaller than the estimated length of PIN
> 551-1 in life-
> c 1.35m.

It is indeed, but it is interesting that it is intermediate in morphology
between the original T. efremovi type and the T. bataar type.


  Which supports the interpretation that Nemegt tyrannosaur specimens represent 
a growth series rather than two or more separate species?



>  Among the most
> > important aspects of this study is the identification of potential
> > synapomorphies with Alioramus remotus (particularly in the region of the
> > nasal-lacrimal-frontal contacts).
>
>  In addition to bones in the rear of the skull?

Yes.  Also, many of the "diagnostic" features of Alio.s braincase are

  Suggests that
> > Alioramus might be a juvenile,
>
>   Based on what, besides its long, low skull?
>
Here's Currie's words:

Alioramus remotus .?Alioramus remotus Kurzanov,1976
is known from only a single partial skull and skeleton col-
lected from Nogon-Tsav in Mongolia.The taxonomic status
of Alioramus is uncertain because of the incompleteness and
immature nature of the specimen.Kurzanov (1976)cited cer-
tain characteristics that were supposedly different than in
other tyrannosaurids.These included the presence of two
conspicuous rows of foramina on the outer surface of the
maxilla,and the position and contacts of the laterosphenoid.
However,these are characters shared with all other tyranno-
saurids.The skull is low because of the small size of the spec-
imen,and ?the greatly elongated jaws ?are typical for all
tyrannosaurid individuals of this size.Other characters ex-
pected in any small tyrannosaurid include the smoothness of
the postorbital bone and the mediolateral compression of the
teeth.The position of the maxillary fenestra falls within the
range of variability for tyrannosaurines like Tarbosaurus .
Although it has pronounced ?hornlets ?on the nasal,they are
comparable in position and number to lower bumps in some
specimens of Daspletosaurus and Tarbosaurus .


   Could the "lower bumps" in certain Tarbosaurus specimens be due to poorer 
preservation?




The prootic
is supposed to surround the trigeminal foramen,but exami-
nation of the specimen suggests that this is probably not cor-
rect.Almost certainly the anterior border of the trigeminal is
formed by the laterosphenoid in the conventional way.The
shape and orientation of the basisphenoid recess is very simi-
lar to these features in Daspletosaurus ,Nanotyrannus ,
Tarbosaurus ,and Tyrannosaurus .Skull proportions suggest
that PIN 3142/1

  Presumably Alioramus, although most PIN 3142 specimens were from Khermeen 
Tsav not Nogoon Tsav.



 might be an immature Tarbosaurus ,al-
though generic distinction is suggested by the higher number
of teeth (16 or 17 maxillary,and 18 dentary teeth),and by the
prominence of the osseous excrescences on the nasal bone.


  Could this "prominence" reflect better preservation?

                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