ANOMALOCARIS GRASPING APPENDAGE
From Chenjiang, China

My favorite!
Anomalocarids were at the top of the
food chain around 490-545 million years ago.
This one is depicted chomping down
with its circular jaw on a trilobite.

Alas, it's nearly impossible to get an
entire fossil of one of these beauties.
They wind up in museum vaults.

Here's an excellent link about it:
http://www.trilobites.info/anohome.html

This beautiful Illustration is from cambrico.galeon.com.