Behind the books
Research leads to fishy new discovery
Bryan Simpson
Issue date: 3/8/10 Section: News
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What these creatures, and others that are immediately thought of, have in common is the fact that they lived on land. So what about those that lived in water?
Well, just ask DePaul University Associate Professor Kenshu Shimada.
Although he is also a vertebrate paleontologist, someone who studies extinct vertebrate animals that lived on land and in water, Shimada focuses his research on sharks or marine vertebrates. Recently, Shimada along with two teams of researchers revealed new information regarding two marine vertebrates that roamed in the same seas during the dinosaur era.
In the Feb. 19 issue of the journal "Science," Shimada and one research team described their discovery of a plankton-eating fish named Bonnerichthys as well as their research on one of these vertebrates.
According to the research, which involved studying the only Bonnerichthys fossil, the large plankton-eating fish survived for about 100 million years, emerging 170 million years ago, and dying-along with the rest of the dinosaurs-65 million years ago.
This is significant because it was previously thought that plankton-eating fish only appeared after dinosaurs became extinct.
However, according to Shimada, modern plankton-eaters, like manta rays and baleen whales, only came into existence because they filled an ecological niche that Bonnerichthys left behind when it died.
In 2008, Shimada first discovered the fin segment of the Bonnerichthys fossil in the Niobrara Chalk Formation of Western Kansas, one area where the Western Interior Seaway passed through over 65 million years ago. Thinking it belonged to a swordfish, Shimada said he expected to find a jawbone with fang like teeth. Instead, Shimada and his colleagues exposed something else.
"The specimen we discovered possessed a long toothless jaw," said Shimada. "It also possessed long gill supporting bones."
Noticing these traits, it was obvious to Shimada that the specimen, which measured almost 20 feet, was a large filter feeder.
"To eat, the fish would open its mouth and ram its body forward, consuming large amounts of plankton and water," said Shimada. "Its gills would then act as a filter, removing the water and keeping the plankton."
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