I already asked this at dinobase but got no answers, I shought I might have more luck here:

I wonder if you can tell me what the latest view is regarding the Tyrannosaurus morphotypes, the gracile and the robust morph. As I understand there where several hypothesies, first of all that the two represent sexual dimorphism or that they might represent geographical variations or simply different growth stages of the same animal. The later actually seems plausible to me since we can see this in many animals including (male) humans, a major difference in bulk between late teenagers and adults but small difference in overall size. But I was mainly wondering about the sexual dimorphism hypothesis since I know of the recent discovery of medullary bone in a T.Rex specimen. That would definately identify it as a female but I couldn't find anywhere the information (or some decent pictures that show) whether the individual was a gracile or a robust morph. According  to the general view the robust Tyrannosaurus was supposed to be the female but if medullary bone where found in a gracile specimen it would cast doubt on that theory. Was medullary bone so far been found only in robust specimens (asumming it was found in more than one specimen)? What is the latest view in the debate about Tyrannosaurus morphs, has a genneral consensous been reached?

MOR 1125, the rex from which this discovery was made, is a robost morphotype. 

It's in the new T. rex volume by Pete Larson and Ken Carpenter.

There's a preview of the correct page here:

http://books.google.co.uk/books?id=5WH9 … ;ct=result

Last edited by Peter Falkingham (22nd Jan 2009 08:49:49)