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Re: Sauropod Biology



Sim Koning (SimKoning@msn.com) wrote:

<The animal seems to be convergent with other high browsing animals, such as
Therizinosaurs and giant ground sloths. Prosauropods had large thumb claws that
would be useful in pulling down tree branches. Since trees don't grow
horizontally, one would expect a Plateosaurus would stand upright at times to
reach high branches. While standing in an upright position, the tail would
obviously rest on the ground, which would help support the weight.>

  There is limited to no evidence any therizinosaur was a high browser. The
typical skeletal restorations done for therizinosaurs tend to use the dorsum
and pelvis of *Nanshiungosaurus* as a model, and then orient the pelvis with
the ilia horizontal, which inclines the dorsal spine upward, but this
orientation is speculative, and so far only *Nanshiungosaurus* shows the high
degree of pelvic rotation that prompts this posture, while the others,
especially *Nothronychus* and *Beipiaosaurus*, show more generalized and
horizontal body postures. 

  Additionally, therizinosaurs possess elongated, non opposing or hooking
digits on long arms, unlike "prosauropods" with their "twist thumbs" and very
robust forelimbs. Despite all this, unlike even sloths, which have short necks
and robust, large enamel-less teeth to process their food with, "prosauropods"
had small, tiny heads on the end of slender necks with many peripheral
blade-like or leaf-shaped teeth. Therizinosaurs and "prosauropods" also share
this teeth arrangement, though in the former the anterior jaws are devoid of
teeth in place of a beak and the teeth are more recurved and bladelike in form,
and in the latter, rostral teeth are more bladelike than they are leaflike, but
the remainder show wear facets that indicate an imbricating bite form, and with
typical herbivorous wear patterns.

  I don't think lumping therizinosaurs and "prosauropods" in the same basket
will help the case.

  Cheers,

Jaime A. Headden

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

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