Fish diversity soars following dinosaur extinction

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The extinction event that killed off the dinosaurs also paved the way for the explosive radiation of the spiny-rayed fishes, according to a study to be published in a forthcoming issue of the Proceedings of the Royal Society B: Biological Sciences.

The spiny-rayed fishes (Acanthomorpha) account for more than 60% of the living bony fishes and almost one-third of all living vertebrates. 

Author Matt Friedman of the University of Oxford used geometric morphometrics to examine morphological diversification within the acanthomorphs, utilizing fossils from the Late Cretaceous (100 million years ago) to the Late Miocene (6 million years ago). 

He found that the anatomical diversity of acanthomorphs is low throughout the Cretaceous, increases sharply and significantly just after the Cretaceous-Tertiary extinction event (the one that killed off the dinosaurs), and then shows little changes throughout the subsequent Cenozoic intervals. 

Although the opportunistic refilling of functional roles once held by non-acanthomorph victims of the Cretaceous-Tertiary extinction event is hypothesised to be a major factor for the rapid radiation of the acanthomorphs, other aspects of morphological diversification cannot be explained by this simple ecological release model, suggesting that multiple factors contributed to the prolific anatomical radiation of acanthomorphs.

For more information, see the paper: Friedman, M (2010) Explosive morphological diversification of spiny-finned teleost fishes in the aftermath of the end-Cretaceous extinction. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2009.2177.