MUTTABURASAURUS IS NOT AN IGUANODONTID

[Tetanurae@aol.com]

After recently finding the original description of _Muttaburasaurus
langdoni_, I extremely speculative and utterly surprised that the describers
announced it as an iguanodontid without question.

Most of the commonly illustrated elements indeed look similar to _Iguanodon_,
but that is because they are mostly reconstructed, if one takes time to
actually look at what was really preserved, one would see that this animal in
truth compares quite closely to basal Iguanodontia like _Tenontosaurus
tilletti_ and _Tenontosaurus dossi_.

The skull, often reconstructed as being some sort of a big-nosed _Iguanodon_,
is in truth very distorted and is missing most of the beak and lower jaws.
 The jugal is massive as in _Tenotosaurus_, but not like _Iguanodon_, and the
quadratojugal is also fairly hefty, unlike the delicate structure in
_Igunodon_.  There also seems to be a prominent nasal crest similar to that
seen in _Tenontosaurus tilleti_.

The scapula is heavily reconstructed, but from the drawings of what is
actually preserved, you can see that it is in fact fairly robust as in
_Tenontosaurus_ and has a distal end similar to that seen in _Tenontosaurus_.
 The corocoids also compare nicely.

One element that compares extremely well to _Tenontosaurus_ is the latterally
sigmoid illium.  The fragmentary prepubis is also very similar.
 Additionally, the latteral maleous of the distal tibia has a very simlar
shape to that seen in _Tenontosaurus_, and to some degree, _Camptosaurus_.

The fragmentary pes has been heavily reconstructed after _Camptosaurus_ to
support a perported close relationship with Iguanodontids, but in truth,
could come from any four-toed ornithischian.

The single element that I believe led the describers to suggest a close
relationship to the Iguanodontidae is a massive spike-like bone that was
interperetted as being the same thing as the thumb-spike in _Iguanodon_.
 This element is not illustrated, and from the description seems to be poorly
preserved, so it cannot be compared to _Iguanodon_ dirrectly, though the
describers state that it is larger than the thumb spike in _Iguanodon_, which
I find a little hard to believe.

In conclusion, from what is known in _Muttaburasaurus_, it seems to compare
more similarly to basal Iguanodotia, than to _Iguanodon_, or _Camptosaurus_,
and it's placement in the Iguanodontidae was questionable at best, based on
ambiguous evidence.

Peter Buchholz
Tetanurae@aol.com

"It's not the heat that gets to me, it's the humidity!"

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REFERENCES:

Bartholomai, A, and Molnar, R E.  1981.  _Muttaburasaurus_, a new
iguanodontid (Ornithischia: Ornithopoda) dinosaur from the Lower Cretaceous
of Queensland.  Memoirs of the Queensland Museum 20(2):319-349.

Forster, C A.  1990.  The postcranial skeleton of the ornithopod dinosaur
_Tenontosaurus tilletti_.  Journal of Vertebrate Paleontology 10(3):273-294.

Norman, D B, and Weishampel, D B.  1990.  Iguanodontidae and related
ornithopods.  Pp 510-533  IN: Weishampel, D B, Dodson, P, and Osmólska, H.
 The Dinosauria.  University of California Press, Berkeley.

Sues, H-D, and Norman, D B.  1990.  Hypsilophodontidae, _Tenontosaurus_, and
Dryosauridae.  Pp 498-509  IN: Weishampel, D B, Dodson, P, and Osmólska, H.
 The Dinosauria.  University of California Press, Berkeley.

Winkler, D A, Murry, Ph A, and Jacobs, L L. 1997.  A new species of
_Tenontosaurus_ (Dinosauria: Ornithopoda) from the Early Cretaceous of Texas.
 Journal of Vertebrate Paleontology 17(2):330-348.