How baleen whales lost their teeth

Modern whiskered whales eat measuredly: they open their mouths, swallow more water, and then filter it through a mustache, leaving all the living creatures on the tongue inside and swallowing it. But their ancestors, apparently, were more mobile and active in finding food. How did they turn from “toothbrushes” into proud owners of a whalebone? The recent discovery of a whale fossil 36.4 million years old sheds light on this.

Mustachioed without a mustache

Researchers discovered a sample in the Pisco basin in southern Peru. Today this fossil is the oldest known member of the suborder Mysticeti, or Baleen whales (these include humpback, greenland, blue and many other types of whales). The ancient whale was 3.5–4 meters smaller than any of its true relatives, but scientists found the most important difference in the skull.

The fact is that modern whiskered whales have special keratin fibers instead of teeth - the very "whiskers" that gave the name to their suborder. They are used as filters, preventing plankton from slipping out of the whale mouth with water. However, the Peruvian find had real teeth, for which it was called Mystacodon. Judging by the skull, this whale was already able to absorb water, as modern whales do, and also feed the young with milk.

Better less, but better.

Mystacodon's teeth show a wear pattern that differs from older whales, basilosaurs. Many basilosaurs were probably active hunters, similar to modern toothed whales (killer whales, dolphins, sperm whales). Their mouths were the perfect weapon to attack.

In the photo: Basilosaurus

At the same time, the mouth of Mystacodon is more suitable for the absorption of small animals. This characteristic of modern baleen whales, plus very real teeth, suggests that scientists have stumbled upon an intermediate link between the two types of feeding and between ancient basilosaurs and baleen whales. Perhaps the reason for this transformation was environmental change: the whale had to adapt to a change in diet.

Universal evolution

Paleontologists found another amazing surprise in the pelvis of a fossil whale: tiny rudimentary hind limbs were preserved in it. Previously, scientists believed that whales lost the articulation of the hip joint even at the stage of basilosaurus, before the evolutionary lines of modern baleen and toothed whales dispersed. That is, "in different rooms" they scattered already full-fledged marine life.

Now it turns out that each suborder lost its hind limbs independently of each other. Another vivid proof of the universal laws of evolution.

Watch the video: How Whales Became The Largest Animals Ever (March 2024).

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