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Re: Erlikosaurus =? Segnosaurus?



>  What characters are present which warrants placing the the two in
>separate genera?

>DSmith.

Here ar some.

Erlikosaurus

The lower jaw is generally shallow, and  the rostral region is curved
downward. Downward  bending is stronger in S.galbinensis than in
E.andrewsi. The dentary is very shallow for most  of its length but is
deeper caudally to form a  slight coronoid promoinence, very low in
E.andrewsi and only slightly elevated in  S.galbinensis. The rostralmost
portion of the  dentary is toothless. In E.andrewsi the tooth row  is
bordered laterally by a shelf starting at the  fifth tooth position and
running to the end of the dentary, suggesting the presence of cheeks. This
shelf is also visible in S.galbinensis, but here  it starts first at the
fourteenth tooth position  and continues baclward only for a half of the
dentary. The large surangular overlaps the caudal  aspect of the dentary.
There is no coronoid and  retroarticular process. The jaw articulation is
set below the line of the tooth row. The external  mandibular foramen is
alrge elongated, and  bordered by the dentary, surangular and angular Source
The Dinosauria by Weishampel, Dodson and  Osmolska.


In E.andrewsi the tooth row  is bordered laterally by a shelf starting at
the  fifth tooth position and running to the end of the dentary, suggesting
the presence of cheeks. This  shelf is also visible in S.galbinensis, but
here  it starts first at the fourteenth tooth position  and continues
baclward only for a half of the  dentary.Source: The Illustrated
Encyclopedia of Dinosaurs by Dr. David Norman

Segnosaurus

Therizinosaurus (Maleev,1954) = Segnosaurus galbinensis (Perle,1979).
Therizinosaurus > T.cheloni formis. 3 specimens, including mandible, pelvis,
hind limb, scapulocoracoid incomplete fore limb, fragmentary vertebrae. The
remains of Segnosaurus were described in  1979 by Dr. Altangerel Perle and
also by Dr.  Rinchen Barsbold (Ulan Bator Mongolia) from  material
discovered during the Sovjet-Mongolian  expeditions. The fossil remains are
incomplete and merely provide an interesting glimpse of other  dinosaur
types. So far the following  Mongolian  Therizinosauridae have been named:
(Segnosaurus ("slow  reptile") scientist concluded that this was the same
animal as Therizinosaurus which was first named.)  Erlikosaurus ("King of
the Dead [Erlik] reptile") Enigmosaurus and an unnamed form, (Alectrosaurus
[2]) all of which come  from the Late Cretaceous Bayn Shireh horizon of
south-eastern Mongolia. Source The Dinosauria by Weishampel, Dodson and
Osmolska.


 The  serrations of the mandibular crowns in  S.galbinensis are more
distinct than those in  E.andrewsi. The teeth in S.galbinensis are placed
somewhat obliquely, so that the serrated mesial  and distal edges are
slightly lingual and labial,  respectively. The entire dentition with the
exception of the first two teeth, is closely  spaced. Wear surfaces are not
observed on the  teeth in E.andrewsi, whereas they are weakly  developed on
the distal edges of some dentary  teeth in S.galbinensis. Source: The
Dinosauria by  Weishampel, Dodson and Osmolska      

                                                                            
                                      

With regards
Fred Bervoets
fb@nrc.nl