It was probably a dominant animal in the seas unless there was a animal bigger then it was in the seas at the time it was alive

The Orca, or killer whale is the top predator at sea, with a wide distribution, and probably the most dominant animal besides humans currently living. The African lion was the second most widely distributed land mammal besides humans. It reached North America and it was found over much of Asia and Europe during the last ice age. The most dominant predator of the ancient world was probably Anomalocaris. It had a world wide distribution, and it has been found in early to middle Cambrian deposits. It was bigger than almost anything found in its time, and could probably eat anything it could find.

ttp://en.wikipedia.org/wiki/Anomalocari...