Sharks deployed high-performance suction feeding as early as 335 million years ago, during the Carboniferous period, according to a new study.

Ray-finned fishes are traditionally credited with developing high-performance suction feeding, while sharks and their relatively primitive jaws have mostly been regarded as morphologically conservative.

Mostly, scientists remain in the dark when it comes to the behavior of early sharks. Cartilage breaks down rather easily. Only teeth and fossil fragments can survive for millions of years. But flattened imprints left by disintegrated shark remains are found in ancient marine deposits.

In a new study, scientists used CT scans and computer modeling to analyze the imprints left by an early dogfish-like shark species, Tristychius arcuatus, in ironstone rock in Scotland. The researchers digitized a variety of fossils from museum collections and compared them to modern fish to better understand how these 2D patterns might translated to three dimensions.

"These new CT methods are releasing a motherlode of previously inaccessible data," Michael Coates, a professor of organismal biology and anatomy at the University of Chicago, said in a news release. "Some of this is superbly preserved. We realized that when we got all the parts out [virtually], we had the complete construction kit to rebuild our shark in 3D."

Their modeling efforts allowed scientists to reconstruct a 3D image of the shark. In addition to physical modeling, researchers used quantitative three-dimensional motion simulation to predict how these primitive sharks might have moved.

Their analysis, detailed this week in the journal Science Advances, showed Tristychius arcuatus deployed a form of suction feeding.

Modern sharks and other fish suck up water through their wide open mouths to capture worms, crustaceans and other seafloor-dwellers. The fish must be able to pull water in through their mouth without pushing it back out. Gills make this possible.

Flexible arches and joints are often deployed by suction feeders to expand cheeks and increase the volume inside the mouth, allowing the fish to pull in more water and create a more powerful suction effect.

The latest research suggests Tristychius sharks had developed all of these anatomical attributes some 335 million years ago. With other sharks relying on the snap of their jaws to capture prey, Tristychius sharks were able to target prey that others were ignoring.

"The combination of both physical and computational models has allowed us to explore the biomechanics in a Paleozoic shark in a way that's never been done before," Coates said. "These particular sharks were doing something sophisticated and new. Here we have the earliest evidence of this key innovation that's been so important for multiple groups of fishes and has evolved repeatedly."

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