A pair of Anomalocaris canadensis appendages. Credit: © Alison Daley
Phys.org has a story about one of the largest predators of the Cambrian Period. Anomalocaris canadensis, which means "weird shrimp from Canada", was first discovered in the 1800's in fossil deposits around Mt. Stephen in British Columbia. Until the discovery of the Burgess Shale, the front appendages and body fossils were thought to be separate animals. A new paper in the journal Proceedings of the Royal Society B looked at the front appendages and concluded they weren't strong enough to crush trilobite exoskeletons. Recent research found the armor-plated, ring-shaped mouthparts of A. canadensis were also probably unable to process hard food. A. canadensis was likely an agile and fast predator, darting after softer prey in open water.
The first step for the research team, which included scientists from Germany, China, Switzerland, the United Kingdom, and Australia, was to build a 3D reconstruction of A. canadensis from the extraordinarily well-preserved—but flattened—fossils of the animal that have been found in Canada's 508-million-year-old Burgess Shale. Using modern whip scorpions and whip spiders as analogs, the team was able to show that the predator's segmented appendages were able to grab prey and could both stretch out and flex.
A modeling technique called finite element analysis was used to show the stress and strain points on this grasping behavior of A. canadensis, illustrating that its appendages would have been damaged while grabbing hard prey like trilobites. The researchers used computational fluid dynamics to place the 3D model of the predator in a virtual current to predict what body position it would likely use while swimming.