Newly investigated fossils show that a type of filter-feeding fishes that aren’t closely related to today’s whales (who, of course, are mammals and not fishes) roamed the oceans during the Mesozoic Era some 170 million years ago. Previously the whales were believed to have been the first large filter feeders, but these new fossils tell a different story. See pictures here

The giant filter feeders, which have been given the name Pachycormiforms, died out at the same time as the dinosaurs. Eventually sharks began filling the vacant ecological niche some 56 million years ago, followed by modern cetaceans such as whales roughly 22 million years later.

The Pachycormiform fossils have been investigated by a team of researchers* led by University of Oxford scientist Matt Friedman, as a part of a study where both old and new fish fossils from England, Japan and the USA have been put under scrutiny. The article has been published in the journal Science.

Some of these fishes were true giants in the world of bony fishes, such as the 6 meter (20 feet) long Bonnerichthys that inhabited a seaway covering what is today the state of Kansas, USA.

A previously described species, Leedsichthys, from the Jurassic of Europe that belongs to the same lineage that includes Bonnerichthys was even larger, likely reaching up to about 30 feet, which is the most massive bony fish of all time,” said Kenshu Shimada, co-author of the article and professor in the Environmental Science Program at DePaul University.

Bonnerichthys was first believed to have been similar to a swordfish, with numerous fang-like teeth.

However, our close examination of the specimen showed that such a long snout and fang-like teeth were not present in the fish,” Shimada said. “Rather, with a blunt massive head, the fish had long toothless jawbones and long gill-supporting bones that are characteristic of plankton-feeding fishes.”

http://www.sciencemag.org

*- Matt Friedman, Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK.

- Kenshu Shimada, Environmental Science Program and Department of Biological Sciences, DePaul University, 2325 North Clifton Avenue, Chicago, IL 60614, USA, and Sternberg Museum of Natural History, Fort Hays State University, 3000 Sternberg Drive, Hays, KS 67601, USA.

- Larry D. Martin, Natural History Museum and Biodiversity Research Center, University of Kansas, 1345 Jayhawk Boulevard, Lawrence, KS 66045, USA.

- Michael J. Everhart, Sternberg Museum of Natural History, Fort Hays State University, 3000 Sternberg Drive, Hays, KS 67601, USA.

- Jeff Liston,Division of Ecology and Evolutionary Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK.

- Anthony Maltese, Triebold Paleontology and Rocky Mountain Dinosaur Resource Center, 201 South Fairview Street, Woodland Park, CO 80863, USA.

- Michael Triebold, Triebold Paleontology and Rocky Mountain Dinosaur Resource Center, 201 South Fairview Street, Woodland Park, CO 80863, USA.