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RE: Therizinosaur track from Denali National Park, Alaska



Referring to oviraptorids at least implies that there is some measure in which 
an oviraptorid pes can reasonably make the print in question. While it is 
possible for a 4-toe impression to be had, for oviraptorids it will have to be 
as deep as it would for a troodontid. Moreover, the dromaeosaurid pes has a 
similar ventral displacement of the hallux with forward alignment (nonreversed) 
(see Norell & Makovicky (1997, 1999), which describe MPC-D 100/985 and 976, 
respectively). Clark et al. (1999, cited by Fiorillo & Adams, 2012) write:

"Metatarsal I articulates on the posteromedial edge of metatarsal II 
three-fourths of the way down its shaft, and is preserved in what appears to be 
its natural position on both feet. Its distal end is twisted anteriorly, so 
that the toe is not reversed as it is in many birds." -- Clark et al. 
1999:pg.11.

If Fiorillo & Adams mean four weight-bearing toes to refer to "forward facing" 
toes, they should be including quite a large range of possible candidates, 
including caenagnathids, troodontids, some odd short-sickled dromaeosaurid, 
etc.. Only therizinosaurids, however, appear to have four _weight-bearing_ 
toes, with hypertrophism of MTI and pdII. In this respect, oviraptorids, nor 
any other four toed theropod, lack the morphology to easily produce the tracks. 
Indeed, the authors write:

"In oviraptorid feet, digits II–IV are the most prominent with the remaining 
digit being reduced to a rodlike structure (Clark et al., 1999; Norell et al., 
2001; Lu¨ , 2005). The digit, if it made contact with the substrate, would 
create impressions very small compared to the impressions left by the other 
three digits." - Fiorillo & Adams 2012:pg.398.

Clark, J. M., Norell, M. A. & Chiappe, L. M. 1999. An oviraptorid skeleton from 
the Late Cretaceous of Ukhaa Tolgod, Mongolia, preserved in an avian-like 
brooding position over an oviraptorid nest. American Museum Novitates 3265:1-36.
Norell, M. A. & Makovicky, P. J. 1997. Important features of the dromaeosaurid 
skeleton: Information from a new specimen. _American Museum Novitates_ 
3215:1-28.
Norell, M. A. & Makovicky, P. J. 1999. Important features of the dromaeosaurid 
skeleton II: Information from newly collected specimens of *Velociraptor 
mongoliensis*. _American Museum Novitates_ 3282:1-45.

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)


----------------------------------------
> Date: Wed, 22 Aug 2012 15:08:27 +1000
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Therizinosaur track from Denali National Park, Alaska
>
> Ben Creisler <bcreisler@gmail.com> wrote:
>
>
> > A bit more about the therizinosaur tracks found in Alaska (in English):
> >
> > http://www.thenewstribune.com/2012/08/21/2263087/6-ton-feathered-dinosaurs-once.html
>
>
> >From the original paper by Fiorillo and Adams, 2012 (open access at:
> http://www.bioone.org/doi/abs/10.2110/palo.2011.p11-083r):
>
>
> "Two groups of theropods that are known to have four forward-facing
> digits are therizinosaurs and oviraptorids."
>
>
> There is at least one other group of Cretaceous theropods that have
> four forward-facing toes. The flightless bird _Patagopteryx_ has a
> "pamprodactyl" foot, with four long, robust digits directed cranially
> (e.g., Chiappe, 2002). _Patagopteryx_ was only about the size of a
> chicken, so it's hard to see how the hallux needed to be recruited for
> weight support. The big, pot-bellied therizinosaurs undoubtedly used
> their enlarged, forward-pointing hallux for weight support. Large,
> flightless, and possibly graviportal birds like _Gargantuavis_ might
> have done the same.
>
>
> Among modern birds, pamprodactyly is seen in certain arboreal birds
> that are specialized for clinging to vertical surfaces like tree
> trunks. The enantiornithean _Rapaxavis_ might also have had a
> pamprodactyl pes - the metatarsal I of this bird is apparently
> straight (O'Connor et al., 2011), not J-shaped as originally described
> (Morschhauser et al. (2009). This means that the large hallux was
> probably directed forward, and argues against anisodactyl perching by
> _Rapaxavis_. Otherwise, the proportions of the foot strongly suggest
> an arboreal lifestyle. Although O'Connor &c don't discuss this, the
> pedal morphology of _Rapaxavis_ makes me think of pamprodactyly, with
> all four toes pointed forward to help support the bird against the
> pull of gravity.
>
>
>
>
>
>
> Cheers
>
> Tim