Was early ungulate first mammal to echolocate?

One of the first mammals to use echolocation may not have been a bat or a whale, but an early ancestor of horses.

Hyopsodus was a weasel-like ungulate that lived 55 million years ago, around the time that bats are thought to have evolved echolocation.

Ma?va Orliac of Montpellier University, France, and colleagues say that a new fossil cast of its braincase shows Hyopsodus had a large inferior colliculus, a brain region enlarged in echolocating animals.

They argue that Hyopsodus could echolocate: a skill that another group of ungulates ? the whales, dolphins and porpoises ? would not acquire for at least another 20 million years.

Gregg Gunnell at Duke University in Durham, North Carolina, says the large inferior colliculus may just be a sign of sensitive hearing rather than full-blown echolocation, though. "If an enlarged inferior colliculus is truly related to echolocation, then Hyopsodus potentially could have used rudimentary sound orientation," he says. "But calling it echolocation seems to be overstating the case."

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0030000

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