Could the following images be a clever hoax? A discarded body part? A species unknown to most? Or an unknown species?

What are your best guesses?

The description with it:

Olesja encountered this on a meadow path near a pond in Bashkiria, Russia. It was about 5 cm long, and had no discernible eyes, legs, or head. It moved in a jerky, almost caterpillar-like motion. She thought it might be a severed lizard tail, but it stopped moving when she touched it, and it resumed moving in the same direction about a minute later. The underside is smoother and darker than the topside.

Thanks to JGodsey.