Parts of it appeared during the latest limb bone extraction. The matrix around that limb bone was particularly nasty, consisting mostly of chert course sand in the limestone matrix. This type really gives me fits since it breaks and dulls the point of the air scribe very quickly. I have to sharpen the bit several times an hour in this stuff. However, the good old-fashioned hammer and chisel remove a lot of this material and I applied my 3 pound hammer and cold chisel liberally.
One big chip took off a flake the size of my palm about 1/2 inch thick (1 cm) and revealed the end to what I assumed was two ribs lying side-by-side. After I removed the limb bone I decided to work a bit on these two 'ribs'. However, after only a few minutes work it became apparent that these were the same bone, with two branches (bifurcation) that had been exposed. It is about 5 inches long, and I don't know how much is still hidden.
Another day's work revealed that this was a substantial bone - but what is it? Here is a picture of one of my better reference skeletons - Midontosaurus Brevis from China. Can you see a bone that looks like this new one? Two candidates come to mind - the interclavical or the lower jaw. However, neither one is a close fit. So we are left with the question - what is it?
I'm actively pursuing this and will be working on it tomorrow and Friday.
Sincerely, Greg Carr