Study unravels why certain fishes went extinct 65 million...(d jaw bones of 249 genera of fossil fish...)

Date:3/26/2009

d jaw bones of 249 genera of fossil fishes that lived during the late Cretaceous. These kinds of direct measurements are possible in fossil fishes because many are represented by complete, articulated individuals. This is unlike the fossil record of most other vertebrates, where bones, teeth and other parts of the skeleton are often scattered and found in isolation.

This study is the first to test this theory with hard data and to quantify the relationship between body size, jaw function and vulnerability of fishes during the Cretaceous extinction, according to Friedman.

"Anyway you sliced it, the data showed that if you were a big fish with a fast bite you were toast," he said.

Ironically, today's large fishes with fast bites evolved relatively shortly after the end-Cretaceous extinction, apparently filling the functional and ecological roles vacated by the victims of that mass extinction. Although the two groups of fishes are not related to each other, their fates may end up being similar.

The paper is called "Ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinction" and will appear in issue 13 of PNAS. In it, Friedman describes the results of his study as robust because the large-bodied, predatory fishes that are disproportionately devastated also have the best fossil records. "In other words, we can be convinced that these forms really do die off here, and that their disappearance can't be chalked up to a lousy fossil record," Friedman noted.

Nevertheless, fossil fishes are not well studied because paleontologists, as a group, tend to be drawn to other animals, such as dinosaurs. Therefore, many large-scale patterns of fish evolution remain unclear.

The fossil fishes included in the study are diverse in form, and range in length from about 20 feet to less than one inch.

"This study demonstrates that fossil datasets are germane to modern diversity and evol
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Contact: Greg Borzo greg.borzo@uchospitals.edu 773-795-0892 University of Chicago Medical Center Source:Eurekalert

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