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Theropod Head Attitude

  Franzosa's Ph.D. thesis of 2004 (U. of Texas, Austin) shows that the
semicircular canals of various theropods are intact, some only at the base, but
these indicate orientation of the labyrinth.

  A horizontal head position is shown in "neoceratosaurs" *Ceratosaurus* and
*Majungatholus*, "carcharodontosaur" *Acrocanthosaurus* inclined its skull down
by about 25 degrees (about the same (~20) in *Diplodocus*), whereas oviraptorid
*Citipati* held its head with the rostrum level with the quadrate condyles.
Franzosa describes what may or may not be semicircular canals around the
floccular lobe in *Byronosaurus*, but these are while intuitively identifiable,
in Franzosa's words they are "debatable"; If we were to use the trace available
for the horizontal sc, the skull would be declined around 30 degrees (tentative
estimate based on tentative evidence). This latter orientation seems to be
roughly 25 degrees (using figures from Brochu, 2000 and Franzosa's own figure).

  Franzosa, J. W. Ph.D. Thesis. _Evolution of the Brain in Theropoda
(Dinosauria)_ (Submitted, 2004, University of Texas, Austin).


Jaime A. Headden

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

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