[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Neimongosaurus and Old-Alectrosaurus Material



Just got this paper (previously mentioned) with the immesurably kind help
of Tracy Ford:

  Zhang X.-h.; Xu X.; Zhao X.-j.; Sereno, P.C.; Kuang X.-w.; and Tan L.
2001. A long-necked therizinosauroid dinosaur from the Upper Cretaceous
Iren Dabasu Formation of Nei Mongol, People's Republic of China.
_Vertebrata PalAsiatica_ 39 (4): 282-290 [w/ pls. I-III].

  Anyways, based on two similarly sized specimens (one slightly smaller
than the other), *Neimongosaurus yangi* is a large animal (2-3 meters,
6.6-9.8 feet) with rather derived humeri (closely-set antebrachial
condyles, large ent- and ectepicondyles), slender yet
very-*Segnosaurus*-ish legs, and a large coracoid tubercle with the
coracoid forming a tight angle from the scapula, though the coracoid is
very large and high. The dentary is derived in that the rostral end is
strongly downcurved and possesses a deep ventral flange that makes the end
appear to be expanded distally. The teeth are very phylodont, and ridges
for the denticles spread onto the crown labially, and are radial to the
median longitudinal axis. This crown appears to be very similar to
ornithischians, in fact. Though restored with a proximal mt-I, the
proximal morphology suggests it was more distally placed, and appears to
be anchored at midlength. The preacetabular ala seems to be oriented
dorsally, twisted at the base as in *Avimimus*, and the fibular crest on
the tibia is more than 50% the tibial length.

  The holotype is LH V0001, part of the newly established Long Hao
Geologic Paleontological Research Center, Hohhot, Nei Mongol Zizhiqu
[Autonomous Region], northeastern China, and was recovered at Sanhangobi,
in Sunitezuoqi, Iren Dabasu Formation, regarded as Senonian, Late
Cretaceous. The type comprises the partial braincase including occipital
plate, and the right rostral dentary with one erupted and several germinal
teeth; post-atlantal cervical sequence, the first four dorsals, and caudal
vertebrae 1-22, with apparently a taper ending with the 25-26 element;
there is a furcula, partial left and even more partial right
scapulocoracoids, both humeri, left radius; partial pelvic gircle
including both partial ilia, femorae, tibiae, distal tarsals 3 and 4, and
most of the left pes, missing the distal intermediate phalanges, and with
unguals. Refered is LH V0008, a complete sacrum with six elements and
partial ilia.

  This hearkens back to 1920, with Gilmore's description of a large
humerus and claws that were refered to *Alectrosaurus* as part of the
holotype. AMNH 6368 includes a right humerus complete except for the
radial condyle and ectepicondylar flange; a proximal manual phalanx that
does not articulate to the ungual, the latter of which is missing the tip.

  I think it's clear what I am suggesting here: the therizinosauroid
material refered to *Alectrosaurus* may pertain to *Neimongosaurus*. Well,
there's some problems. The two known humeri are different in size, and
that of the larger, AMNH material (39cm) has a less medially inclined
humeral caput. The LH specimen (not to be confused with the Las Hoyas
material, which also use that abbreviation), at 22cm, may very well have a
different morphology at greater size, but it seems the mediolateral
proximal width of the humerus are the same between specimens. Greater
length may equate without greater width of the proximal end. The caput is
perpendicular at 90 degrees in the LH specimen, but greater (inclined
dorsally) in the AMNH specimen. In most therizinosauroids, including
*Neimongosaurus*, the deltopectoral crest distally traverses the humeral
shaft, but in the AMNH specimen it does not. If it is a therizinosauroid,
as previously suggested (Mader and Bradley, 1989), rather than a
tyrannosaur (Gilmore, 1920), then it does not appear to be the same as
*Neimongosaurus*.

  Gilmore, C.W. 1920. On the dinosaurian fauna of the Iren Dabasu
Formation. _Bulletin of the American Museum of Natural History_ 67: 23-78
[w/ pls. I-VIII].
  Mader, B.J. and Bradley, R.I. 1989. A redescription and revised
diagnosis of the syntypes of the Mongolian tyrannosaur Alectrosaurus.
_Journal of Vertebrate Paleontology_ 9(1) 41-55.

---

  I find it very interesting that the Benton et al. supertree found a
sister-group relationship between *Microraptor* and *Elmisaurus*, given
that they do not share any material aside from scattered manual elements,
and they are not enough to suggest a closer affinity than with any other
taxon. Peculiar, though....

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

__________________________________________________
Do You Yahoo!?
LAUNCH - Your Yahoo! Music Experience
http://launch.yahoo.com