Its unusual, O-shaped mouth was composed of 32 overlapping plates and protected by two spiky prongs that hung down from its face.

Scientists had assumed the well-armored mouth could crush and feed on other hard-shelled organisms. For instance, the ancient beast was thought to feast on organisms such as trilobites, segmented invertebrates that also lived on the seafloor.

(Related picture: "Biggest Trilobite Sea Beasts Found ... in Swarms."

But paleontologist James "Whitey" Hagadorn, of the Denver Museum of Nature & Science, and his team may have quashed this theory using a 3-D computer model of the creature's mouth.

"We're basically saying that Anomalocaris may not have been