Figure 1: A pile of these strange rocks.
How the Rocks Were Found
While on a fossiling trip in the Horseshoe Canyon Formation Back in April of 2025, We stumbled upon this really pile of weird rocks (Figure 1). It didn't match it's surroundings and had a shiny interior (Figure 2). Some of them even had a few pieces of bone on them. Initially I thought that it was a coprolite, and after doing some research, it did look similar to some coprolites. It wasn't until the next few fossiling trips that my doubts about this being a coprolite grew, as I found more of the same rocks in other places near the place that we found the first one. There was no way I could be this lucky and find that many coprolites.
Figure 2: A specimen of the strange rock.
So What Actually is This Rock?
After asking some questions, I got a much better idea as to what this mysterious rock might be. Atharva Roy, a member of the Alberta Palaeontological Society had found similar rocks. He said that it could be agatized bone, and that it may have been eroded out of the ground during the cretaceous and then was buried again later on making it poorly preserved. Or that it could have just been poorly preserved from the start. Coprolites are quite rare to find in the Horseshoe Canyon Formation, so if this was one then that would have been an awesome find!
Figure 3: Albertosaurus in the Horseshoe Canyon Formation.
Why are Coprolites Rare in the Horseshoe Canyon Formation?
Atharva Roy stated that the soils of the Horseshoe Canyon Formation were acidic when they were deposited. Therefore certain things like eggshells and coprolites likely didn't preserve well. So if you do manage to find a coprolite in the Horseshoe Canyon Formation it's even more special! Atharva has an example of a coprolite on his Instagram! I would also like to thank Atharva for all the help with identifying this mystery rock!