If you didn't figure out it's the skin of a snake, go ahead and smack yourself on the forehead now (and be careful if you go out in the woods).
You get two points if you guessed "rattlesnake." Check out the full image, with rattle, below. Meantime, some cool facts:
To create that chill in your spine a rattlesnake's rattle moves back and forth about 60 times a second. The rattle's segments are formed more than once a year, each time the snake sheds its skin. And they sometimes break off. So it's a myth that you can tell a rattlesnake's age by the number of segments in its rattle.
If you're one who feels that chill just at the thought of snakes, you're not alone. Many people fear snakes, and scientists think humans may have evolved an innate tendency to sense snakes — and spiders — and to learn to fear them, because in fact they can be dangerous.