What’s the quietest thing you’ve ever noticed in a fossil?

I was prepping a juvenile Hesperonychus last week, and for twenty minutes I swear I heard nothing but the sound of my own breath. Then, right at the base of the ilium—just a hairline fracture that didn’t even register on the CT scan—I found a microscopic groove. Not wear, not pathology. Something like a memory of movement. I don’t know what it means. But I’ve been thinking: what tiny thing has ever made you stop and say, ‘Wait… that wasn’t there before’?