Parapontoporia The common dolphin, an extinct genus of long-nosed dolphins that lived along the Pacific coast of North America from the late Miocene to the Pliocene, was likely able to hear in a narrow band of high-frequency sounds, a new analysis has found. Parapontoporia The bony labyrinth.
“Whales, dolphins and porpoises (cetaceans) represent one of the most dramatic transitions in the history of mammals: a return from land to water,” said researchers Dr. Joyce Sanks of Vanderbilt University and Dr. Rachel Racicot of the Senckenberg Institute and the Natural History Museum.
“As a result, this group acquired a series of aquatic adaptations, such as moving their nostrils to the top of their heads and streamlining their bodies.”
“Echolocation developed early in the evolutionary history of Oligocene toothed whales (Odontoceti), and all modern toothed whales possess this ability.”
“The biosonar clicks produced by most extant toothed whales typically cover a wide frequency spectrum, from tens of kilohertz to 150-170 kHz.”
“Conversely, certain toothed whales emit characteristic biosonar clicks that have narrow bandwidth but high centroid frequencies.”
“These distinctive clicks have a peak frequency of 125-140 kHz and a bandwidth of 11-20 kHz.”
Using high-resolution x-ray CT scans, the authors examined the inner ears of three people. Parapontoporia Two specimens, Parapontoporia sternbergii and Parapontoporia pacifica From the collection of the San Diego Natural History Museum.
With the help of 3D models, the team was able to prove that these creatures already had narrow-band, high-frequency hearing during the Miocene epoch, about 5.3 million years ago.
“Echolocation, as used by animals, also developed quite early in evolutionary history,” Dr Racicot said.
“The animals emit sound waves that bounce off objects and send back echoes, providing information about the object's distance and size. All toothed whales currently use this natural sonar system.”
“Echolocation is a rational hunting and communication strategy, especially in the ocean, where sound travels five times faster than in air, and where visibility is often reduced.”
“What's particularly interesting is that these dolphins have once again changed habitat, leaving the marine environment to colonize rivers.”
There are still a few dolphins living in the river today, with all six species now extremely rare and endangered.
As a relative Chinese river dolphin (Lipotes vexilifer) Last recorded in 2002, Parapontoporia It provides insight into the transition from marine habitats to freshwater environments.
“We speculate that this early and widespread evolution of echolocation in the dolphins we studied was driven by selective pressure or ecological advantage,” Dr Racicot said.
“River systems are spatially complex habitats, and this form of orientation and communication would likely have been advantageous for long-nosed dolphins.”
“Further research into toothed whales' sensory organs could be an important tool for studying the influence of habitat on cetacean hearing and for understanding the evolutionary dynamics of marine mammals.”
of result Published in this month's journal Anatomy record.
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Joyce Sanks & Rachel Racicot. Biology and prediction of hyperacusis. Parapontoporia – The extinct fin whale. Anatomy record Published online July 15, 2024; doi: 10.1002/ar.25538
Source: www.sci.news
