Smithsonian scientists and colleagues report a new study that may shake up the way paleontologists think about how environmental change shapes life on Earth. The researchers summarized the environmental, ecological and evolutionary consequences for Caribbean shallow-water marine communities when the Isthmus of Panama was formed. They concluded that extinctions resulting when one ocean became two were delayed by 2 million years.
Researchers from the Smithsonian Tropical Research Institute, Scripps Institution of Oceanography and London's Natural History Museum report their study in the Proceedings of the National Academy of Sciences on March 12.
Three to 4 million years ago, the Isthmus of Panama land bridge rose to connect North and South America, and divided one vast ocean into two. In response, a major extinction of marine animals that had flourished under open seaway conditions occurred on the Caribbean side of the new Isthmus.
"We may be way off-track when we search for the causes of extinctions by looking only at the time the extinctions occur in the fossil record, which is what paleontologists normally do," said Aaron O'Dea, postdoctoral fellow at the Smithsonian Tropical Research Institute and Scripps Institution of Oceanography. "In our case, we see that most coral and snail species died off a good 2 million years after the environmental change that caused their demise."
The researchers don't yet know why extinction was delayed for such a long time. According to O'Dea, the species probably underwent severe reductions in their abundances and geographical ranges but managed to cling on until some sort of threshold was reached.
O'Dea said the results suggest paleontologists may need to dig deeper when searching for the causes of the great events in the history of life. "The results also may be taken as a warning because right now we are seeing similar reductions in ranges and abundances of many animals and plants due to a
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