Estimating Hip Heights

[Jaime Headden <qi_leong@hotmail.com>]

Senter, P & Robins, H. J. 2010. Hip heights of the gigantic theropod dinosaurs 
*Deinocheirus mirificus* and *Therizinosaurus cheloniformis,* and implications 
for museum mounting and paleoecology. _Bulletin of th Gunma museum of Natural 
History_ 14:1-10.
 available online at: 
http://www.gmnh.pref.gunma.jp/research/no_14/bulletin14_1.pdf

 Abstract:
 "The gigantic theropod dinosaurs *Deinocheirus mirificus* and 
*Therizinosaurus cheloniformis,* from the Upper Cretaceous Nemegt Formation of 
Mongolia, are known only from bones of the forelimb and pectoral girdle. They 
possess the longest known forelimbs among theropods. To determine whether the 
lengths of forelimb elements have predictive value for the length of the 
hindlimbïHL = length of femur + tibia + metatarsal IIIï, we computed Spearmanâs 
Rank Correlation Coefficients for HL versus various forelimb bones in 
ornithomimosaurs, theropods in general, and bipedal dinosaurs in general. We 
found that scapular length and humeral length correlate welïl> 90%ï with HL in 
all three samples, but lengths of the radius and second metacarpal do not. 
Using regressions of scapular length à HL and humeral length à HL we find that 
HL is 3323.14 - 3646.50 mm for *D. mirificus* and 3001.10 for *T. 
cheloniformis.* These two animals have the highest HL in the dinosaur fauna of 
the Nemegt Formation, and *D. mirificus* has the highest HL of any theropod. 
Contemporaneous tyrannosaurids could bite no higher than their bellies and 
thighs, and other contemporaneous predators were too small to have preyed upon 
them. If *D. mirificus* and *T. cheloniformis* were browsers and 
contemporaneous herbivores cropped vegetation with the neck in the 
osteologically neutral position, these two theropods would have competed for 
foliage only with each other."

 Comparatively, *Deinocheirus* was as tall at the hip as was *Tyrannosaurus 
rex*, while *Therizinosaurus* was shorter. Among theropods, they are they 
tallest (at the hip). As some have shown, including Paul, the posture for 
*Therizinosaurus* would have likely inclined the body upwards at the hip at it 
seems to have done for *Nanshiungosaurus* (the next biggest therizinosauroid), 
and this would have made *Therizinosaurusd* the tallest theropod on record. 
*Deinocheirus* is a little trickier: ribs are known for *Deinocheirus* 
(Osmolska and Roniewicz, 1970), but they are poorly distinguished from the 
pectoral girdle and forelimb; it has also been questioned that *Deinocheirus* 
is an ornithomimosaur, which makes comparing regressions a little harder 
directly, but fortunately Senter and Robins avoided this by using a mean of 
theropods rather than just ornithomimosaurs.

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)

                                          
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