Dinosaur Ridge

[Rockwood]

This is in the rocks near labeled dinosaur bones at Dinosaur Ridge, west of Denver in Colorado.

When I took the photo I  just assumed it was a transsection of a long bone. I've become less certain of it each time I look at the photo though. 

[ynot]

Cross section of a concretion to Me.

[Tidgy's Dad]

Yes, looks like a concretion to me as well, I'm afraid.

[Rockwood]

1 hour ago, Tidgy's Dad said:

I'm afraid.

No need. My vacation trips are so condensed that it's become my strategy to take a picture now, figure it out later anyway.