At MSNBC (5/25/20), Charles Q. Choi tells us “Bizarre shrimp-like predators grew larger and survived longer than thought”:
The creatures, known as anomalocaridids, were giant predators (ranging from 2 to possibly 6 feet in length) with soft-jointed bodies and toothy maws with spiny limbs in front to snag worms and other prey.
[ … ]
Past research showed they dominated the seas during the early and middle Cambrian period 542 million to 501 million years ago, a span of time known for the “Cambrian Explosion” that saw the appearance of all the major animal groups and the establishment of complex ecosystems.
A normal length is actually about three feet, but this find is interesting I view of the fact that we are accustomed to thinking of Cambrian creatures as rather small. They also lasted much longer than expected.
File under: Bigger than expected, earlier than expected, around longer than expected, expect the unexpected.