Fossil hunters say they have unearthed a missing link in the evolution of baleen whales after digging up the remains of a creature thought to have lived more than 36 million years ago.
(From The Guardian) — The whales, known as mysticeti, sport a bristling collection of sieve-like plates known as baleen that they use to filter water for food. Species include the enormous blue whale, the gray whale and the humpback whale.
But while baleen whales are known to have shared a common ancestor with toothed whales, which are the other major group of modern whales, the path by which the creatures emerged has been somewhat hazily understood. Now researchers say they have discovered the oldest known cousin of modern baleen whales, offering unprecedented insights into their evolution.
“This [split in the family tree] has been dated to about 38 or 39m years ago,” said Olivier Lambert, co-author of the research from the Royal Belgian Institute of Natural Sciences. “The whale we discovered here has been dated to 36.4 [million years ago], so it is only two to three million years younger than this presumed origin.”
Unearthed at a site known as Playa Media Luna on the southern coast of Peru, the newly discovered creature has been named Mystacodon selenensis – a portmanteau of the Greek for “moustache” and “tooth”, together with a nod to the Greek goddess of the moon.
The animal would have been just under four metres in length but, rather than boasting baleen, it had a mouthful of teeth and apparently vestigial hind limbs.
From an analysis of the skull, jaw and teeth, Lambert says that the newly unearthed animal likely hoovered up other marine creatures by suction feeding, moving its tongue to lower the pressure inside its mouth and draw its prey in, before expelling the water.
“If it was indeed using suction to catch its prey, it means that the prey items could not be too large, because the whole animal was swallowed in a single gulp – so medium sized fish, maybe small squid, could have been a good type of prey for such an animal,” he said.
By contrast, the ancestors of both baleen and toothed whales are thought to have captured prey by grabbing it with their teeth, a method also used by many modern toothed whales.