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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Come On In, the Water's Fine
24 July 2008 (All day)
From a sweltering Jacuzzi to a tepid bath. When the world's oceans experienced such a drop in temperature almost a half-billion years ago, life exploded. Ancient arthropods like the trilobites and their neighbors were soon overwhelmed by new legions of shelled beings in the sea. That's the conclusion of a study appearing tomorrow in Science, which may finally solve the mystery of this unprecedented diversification of animal life.
The Great Ordovician Biodiversification Event--or more modestly, the Ordovician radiation--was an uncomfortably warm, possibly scalding, time. At least that's what some research had indicated. Scientists applied a thermometer to the period by measuring the ratio of heavy to light isotopes of oxygen in 470-million-year-old carbonate shells belonging to stalked animals called brachiopods. The ratio varies depending on the temperature of the water in which the shells formed, and the data indicated unreasonable ocean temperatures of up to 70°C.
Paleontologist Julie A. Trotter of Australian National University in Canberra wondered whether the fossils were the problem. Perhaps their oxygen ratio had changed over time. So she and her colleagues analyzed the more durable fossil mineral phosphate in the form of the toothlike remains of a now-extinct eel-like animal. Across the 44-million-year-long Ordovician period, they found ocean temperatures steadily declining from a steamy 42°C (5°C higher than human body temperature) to a plateau of about 30°C, which is typical of the modern sea surface on the equator.
Not coincidentally, the group contends, the attainment of a modern balminess in the Ordovician coincided with the heart of the animal explosion. Corals, for example, could survive only under the cooler temperatures, Trotter says.
The new temperatures seem reasonable, says geochemist John Eiler of the California Institute of Technology in Pasadena. "If you had to bet, you would say these guys have [the temperature] right." And "if this cooling really did happen,” says paleontologist Arnold Miller of the University of Cincinnati, “it had to have some effect on biodiversity." Miller suspects, however, that the radiation had more than one cause, and this one needs a lot more testing.