The Lileep-Cradily evolutionary line of Pokemon are based on crinoids, also known as sea lilies.

Fossil evidence shows us that creatures such as sea urchins began to view the stationary sea lilies as an easy meal: many crinoid fossils from the Triassic period show evidence of teeth-marks! It seems that this is why some crinoids became motile again. Some, such as the feather stars, have become reasonably adept swimmers: not especially quick or graceful, but enough to make a break for it if things seem to be getting dangerous. Other species have been seen to slowly walk along the sea floor using their multiple arms. This gradual progression towards motility seems to be referenced in the Pokédex entries of Lileep and Cradily, too... while Lileep is stated to be immobile, numerous references are made to Cradily moving around (albeit inelegantly).