Photo: Sound is produced by Echovenator sandersi, which bounces off prey to create echoes. This illustration shows how these echoes are detected via conduction of vibrations through the mandible and received by the whale's inner ear. Credit: A. Gennari 2016.
A new whale species with the name "Echo Hunter" (Echovenator sandersi), for its super-hearing, has just been described, and it's helping researchers gain new insight into the evolution of high-frequency hearing in the the earliest whales.
The finding comes thanks to a fossil, dated to 27 million years ago, that includes a highly-intact skull. It was examined by researchers from the New York Institute of Technology (NYIT), who got the chance to study what they say is one of the most well preserved fossils ever found of a whale's ear.
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And what an ear. Aided by uniquely shaped inner ear structures, the whale could hear sounds far outside the range of human ears.
"This was a small, toothed whale that probably used its remarkable sense of hearing to find and pursue fish, with echoes only," explained study co-author Jonathan Geisler, an NYIT associate professor, in a statement.
High-frequency hearing capability is a necessary feature of all toothed whales, which use it in conjunction with echoes of their own calls in order to echolocate – using sound to map out their surroundings and navigate and seek food. Bats use it. So do dolphins.
"This would allow it to hunt at night," said Geisler. "But, more importantly, it could hunt at great depths in darkness, or in very sediment-choked environments."
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The NYIT researchers say their study shows that most of the features for high-frequency hearing in the animals were in place 27 million years ago, around the same time that echolocation evolved. Some features might have even evolved earlier than that.
"Previous studies have looked at hearing in whales but our study incorporates data from an animal with a very complete skull," said postdoctoral fellow Morgan Churchill, the lead author of the study.
"The data we gathered enabled us to conclude that it could hear at very high frequencies," he noted, "and we can also say with a great degree of certainty where it fits in the tree of life for whales."
Detailed findings about the new species and its hearing have been published in the journal Current Biology.
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