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Horses buck evolutionary ideas

Speciation events not accompanied by big changes in teeth and body size

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2:00pm, February 9, 2017
horse evolution

HORSE RACE  As ancient horses rapidly diversified into new species, drastic changes in body size didn’t occur, despite the diversity found in the fossil record, a new analysis shows. (Three species from roughly 8 million years ago are shown.)

A cautionary tale in evolutionary theory is coming straight from the horse’s mouth. When ancient horses diversified into new species, those bursts of evolution weren’t accompanied by drastic changes to horse teeth, as scientists have long thought.

A new evolutionary tree of horses reveals three periods when several new species emerged, scientists report in the Feb. 10 Science. The researchers found that changes in teeth morphology and body size didn’t change very much during these periods of rapid speciation.

“This knocks traditional notions that rapid diversification of new species comes with morphological diversification as well,” says paleontologist Bruce MacFadden of the University of Florida in Gainesville. “This is a very sophisticated and important paper.”

The emergence of several new species in a relatively short time is often

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