Re: Labocania anomala

["Jaime A. Headden" <qilongia@yahoo.com>]

Dann Pigdon (dannj@alphalink.com.au) wrote:

<Indosuchus was originally thought to be tyrannosaurid as well. And yet
abelisaurs and tyrannosaurs don't seem to be all that closely related.
What is it about the two groups that seems similar?>

  Both groups sport reasonably similar skulls. They both have a thickened
skull roof, a mediolaterally robustly thickened maxilla and premaxilla, a
robust dentary, fused interdental plates with virtually no distinction
between septa and the medial or lateral dentigerous walls; they both have
roughened texturing of the facial bones or nasal. They have large scapulae
with small arms. The orbit invariably forms an elongated "kidney" shape
thanks to the postorbital having a process invading it. The premaxillary
teeth are generally small and have D-shaped cross-sections, though to a
greater degree in tyrannosaurids, in non-tyrannosaurids, D-shaped teeth
are similar in abelisaurids, some allosaurids, tyrannosauroids in general,
etc. (i.e.,  most "large carnosaurs" or large theropods appear to have
similar cranial specialization to "nip" meat out, so their teeth follow
this trend). Heavily-built, robust skull bones with ornamentation seems to
be prevalent, as it is seen in some "carnosaurs," tyrannosauroids, and
abelisaurids fairly commonly. This may allow isolated or "robust" elements
to be seen as either abelisaurids and tyrannosaurids, so may lead to the
mistaken use of *Labocania* as a tyrannosauroid. This is ignoring the
postcrania, which may tell another story.

  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.

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


        
                
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