A top predator approximately 540 million years ago was an over two-foot-long shrimp relative that was the first known actively swimming filter feeder, according to the latest issue of Nature.
It was perhaps the most peaceful time on the planet, since the shrimp-like animal, Tamisiocaris borealis, had no predators and did not have to chase and attack prey.
“It is unlikely that there was anything that hunted Tamisiocaris,” lead author Jakob Vinther told Discovery News. “It was among the largest animals of its time. Therefore, it could calmly swim around and eat like a gentle giant without feeling the slightest hint of a threat, just like modern whale sharks (do today).”
New fossils of the creature, collected from early Cambrian (485–540 million years ago) sediments in northern Greenland, provide a detailed look at its anatomy. T. borealis was an anomalocaridid. These were marine animals that later gave rise to arthropods, a group that includes shrimps, other crustaceans, spiders and insects.
Previously, it was thought that the huge shrimp-like animal grabbed prey and shoved victims into its relatively big mouth. Analysis of the new fossils negates that scenario.
“They used the fine mesh of bristles on their feeding appendages for trapping small planktonic crustaceans, similar to water fleas or sea monkeys,” Vinther, a lecturer in macroevolution at Bristol University, explained.
“By sweeping the net-like or comb-like appendages through the water, almost like a butterfly fancier would do on a meadow, it gathered the teeming schools of little crustaceans and moved them up to its mouth where they would get sucked in.”
Before this research, scientists didn’t think oceans were teeming with life during the early Cambrian. Fossil evidence suggested that a lot of animal activity was happening on sea floors, but that the water column itself was sparsely populated. T. borealis and some other recent finds change that theory.
Filter feeding itself would not be possible if the water wasn’t full of little organisms to eat.