artists reconstruction of Tamisiocaris borealis
March 27, 2014

Early Cambrian Arthropod Used Large Curly Appendages For Feeding

Brett Smith for - Your Universe Online

Several large marine animals have evolved from fearsome predators to become gentle giants that use filtering appendages to ingest food, and new research from a team of European researchers has revealed a similar evolution in a group of predators that roamed the oceans 520 million years ago during the Early Cambrian.

According to the team’s report in the journal Nature, an early arthropod called Tamisiocaris borealis used large curly appendages in front of its mouth to filter food from the water and sweep the entrapped prey into its mouth. The predator belongs to an ancient group of marine predators that used to dominate the Cambrian seas called anomalocarids.

"These primitive arthropods were, ecologically speaking, the sharks and whales of the Cambrian era,” said study author Jakob Vinther, a lecturer in macroevolution at the University of Bristol in the UK. “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 study team discovered fossils of T. borealis and its unique appendages while on an expedition in a remote corner of Greenland during the summer, a place and time of year when the sun doesn’t set. On the expedition, the team said they would simply sit on the side of a hill and split open long, flat rocks in search of fossils.

"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 still waiting to be described," said study author David Harper, a professor at Durham University.

Based on the fossils, the researchers were able to create a three-dimensional computer animation of the animal’s feeding appendage to determine its potential range of movements.

"Tamisiocaris would have been a sweep net feeder, collecting particles in the fine mesh formed when it curled its appendage up against its mouth," said Martin Stein of the University of Copenhagen, a study author who created the computer animation. "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."

The study team said their discovery reinforces the diversity found throughout the Cambrian, with different species of anomalocaridids prowling the sea and rapidly evolving during that time. The scientists said the find also provides more details on the ecosystems that existed half a billion years ago.

"The fact that large, free-swimming suspension feeders roamed the oceans tells us a lot about the ecosystem," Vinther said. "Feeding on the smallest particles by filtering them out of the water while actively swimming around requires a lot of energy – and therefore lots of food."

"We once thought that anomalocarids were a weird, failed experiment," said co-author Nicholas Longrich at the University of Bath. "Now we're finding that they pulled off a major evolutionary explosion, doing everything from acting as top predators to feeding on tiny plankton."

"Our new understanding of this remarkable animal adds another piece to a fascinating jigsaw puzzle,” Harper added.

Image 2 (below): This is one of the fossil feeding appendages of Tamisiocaris borealis, an anomalocarid that lived 520 million years ago during the Early Cambrian. A new study of Tamisiocaris fossils discovered in northern Greenland has found that these ancient marine animals used bizarre facial appendages to filter food from the ocean. The research, led by the University of Bristol, UK, is published this week in Nature. Credit: Jakob Vinther, University of Bristol