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Re: An Odd Question on Tyrannosaurs.....





Were their sterna articulated with, or in the proximity of, the coracoids?

In life, certainly.


Well sure! I was just wondering about their placement in relation to the coracoids when the animals were actually found in the ground. The only paper I have that out right mentions the sterna is the 1998 JVP one by Currie and Makovicky, that you also mentioned. It doesn't give the positions for which they were found fossilized. Doesn't matter really anyway.

The 1998 JVP paper on tyrannosaurid furculae has shown that there was nothing between the coracoids because the coracoids touched, that's the only thing furcula and sternum were broad enough for. There remains a bone-free triangle between sternum and coracoids, however; maybe a cartilaginous extension of the sternum was in there.


Looks like I goofed in my wording at 4am. Instead of saying between the coracoids, I should have copied verbatim this line from that SVP paper: "The sternum in tyrannosaurids (Lambe 1917) would have been posterior to and between the coracoids as in oviraptors and Carnotaurus (Bonaparte et al.. 1990)." Woops...... I forgot a word.  I always followed Mr. Paul's suggestion about the coracoids abutting along their ventral line too. And yes, I'm betting that the supposed upside-down heart-shaped triangular space was probably filled with an extension of cartilage off of the sterna. What I was at a bit of a loss about is to what extent did we actually know of the state of the sterna in tyrannosaurs. Sure, the JVP paper explains how they probably attached to the coracoids, and it says that the sternal plates wopuld have been smaller relatively speaking, then in dromaeosaurs etc. But, it didn't really tell me what we knew for sure... As in if we actually had pe! rf! ! ectly complete sterna that looked and fit as the paper indicated. The closest thing to doing so was figure 5 in the paper of the shoulder girdle in anterior view. I knew we had something, but I was mostly curious about the degree in ossification of the known sterna. (minus the costal cartilage attaching it to the ribs). I have never come across anything giving me a clear cut answer.... Hence why I defaulted to saying cartilaginous.

Let's just say I'm trying to cover all the bases.

So, this little sterna issue has been pretty much cleared up for me now. We have some that we can say were completely ossified...... completely bone. I can run with that just fine. Now I need some thoughts on the airsac extent in tyrannosaurs, along with further clarification on the possibility of any type of marks found on their ribs that could be interpreted as attachment points for unossified unicates.... Would there even be any marks for them if they were present in the first place?... Depending on how extensive we propose the airsac system was, would tyrannosaurs had even needed them to aid in ventilation? These are the things I'm still a bit in the dark about.

Thanks again Mr. Marjanovic.

Kris