Do you have something that flowered and went to seed nearby?

I had a yellow flag iris do something similar. I thought I had cut all the seed pods off but missed one.

Actually, no.
It's more like something that emerged out of the ground.

Please tell us the size of individual "nubbins."
Also describe their texture: sot/ brittle? rock hard? or what?
And what plant/plants is it associated with?

Do you have some type of Arum growing there? Sometimes known as Voodoo Lily.
Mike

animal skat?

I've seen "fairy cups", a kind of fungus, make something similar to this in growth pattern. Do these seem like they are boiling up out of the ground? It might be something like that then. Fairy cups are kind of like a mushroom, which when they are ripe open up into a cup shaped arrangement, with the spores in the center being splashed out in the rains as the drops enter the cup and splash the contents out and around. Pretty cool biology, actually. The ones I am familiar with love cardboard, and are plentiful after sheet mulching. But the ones in your picture look hard and shiney, very different from the ones I am familiar with. But the overall look of the little nubs coming up looks very similar?

In the picture posted here they do like like they may be popping open, in the manner of puff balls.