When times are good, it pays to be the big fish in the sea; in the aftermath of disaster, however, smaller is better.
According to new research led by the University of Pennsylvania's Lauren Sallan, a mass extinction 359 million years ago known as the Hangenberg event triggered a drastic and lasting transformation of Earth's vertebrate community. Beforehand, large creatures were the norm, but, for at least 40 million years following the die-off, the oceans were dominated by markedly smaller fish.
"Rather than having this thriving ecosystem of large things, you may have one gigantic relict, but otherwise everything is the size of a sardine," said Sallan, an assistant professor in Penn's Department of Earth and Environmental Science in the School of Arts & Sciences.
The finding, which suggests that small, fast-reproducing fish possessed an evolutionary advantage over larger animals in the disturbed, post-extinction environment, may have implications for trends we see in modern species today, such as in fish populations, many of which are crashing due to overfishing. The research is reported in Science.