Early arthropods evolved into filter feeders

Newly discovered fossils of marine animal Tamisiocaris suggest the early arthropod evolved into suspension feeders to filter plankton, much like modern day whales. Evidence pointed to the animal swimming with flaps down either side of their body, with large appendages in front of their mouths most likely used to capture larger prey like trilobites. However, the new fossils – discovered in North Greenland – show the animals evolved into suspension feeders, with their grasping appendages morphing into filtering apparatus that could be swept like a net through the water, trapping small crustaceans and other organisms. “We once thought that anomalocarids were a weird, failed experiment,” said Dr Nick Longrich from the University of Bath’s Department of Biology and Biochemistry. “Now we’re finding that they pulled off a major evolutionary explosion, doing everything from acting as top predators to feeding on tiny plankton.” Dr Martin Stein from the University of Copenhagen created 3D computer animations to model how the animal might have fed. “Tamisiocaris would have been a sweep net feeder, collecting particles in the fine mesh formed when it curled its appendage up against its mouth,” he said. “This is a rare instance when you can actually say something concrete about the feeding ecology of these types of ancient creatures with some confidence.” [caption id="attachment_37833" align="alignright" width="200"] One of the fossil feeding appendages of Tamisiocaris. Credit: Jakob Vinther, University of Bristol[/caption] Tamisiocaris belonged to a group of animals called anomalocarids, which included some of the largest and most iconic animals of the Cambrian period. They lived 520 million years ago during the Cambrian Explosion in which all the major animal groups and complex ecosystems emerged. “These primitive arthropods were, ecologically speaking, the sharks and whales of the Cambrian era,” said Dr Jakob Vinther, a lecturer in macroevolution at the University of Bristol, and lead author of the study published in Nature. “In both sharks and whales, some species evolved into suspension feeders and became gigantic, slow-moving animals that in turn fed on the smallest animals in the water.” The discovery not only sheds light on the evolution of Tamisiocaris, it also shows how productive the Cambrian period was. “The expeditions have unearthed a real treasure trove of new fossils in one of the remotest parts of the planet, and there are many new fossil animals waiting to be described,” said Professor David Harper from the University of Durham. “Our new understanding of this remarkable animal adds another piece to a fascinating jigsaw puzzle.” A suspension-feeding anomalocarid from the Early Cambrian 3D computer animation showing how Tamisiocaris could have used its strange appendages to feed (Credit Dr Martin Stein) http://youtu.be/3aLd8NN0YtY