Three-dimensional model of an ancient whale skull.
What’s the News: Scientists have long held that archaeocetes, the precursors to modern cetaceans, had symmetrical skulls like most other mammals. Whale skulls only became asymmetrical as certain species evolved echolocation to hunt for food. But it turns out that archaeocetes actually had skewed skulls, which likely allowed the whales to hear better underwater, according a new study published in the journal PNAS.
What’s the Context:
- Modern whales fall into two groups: toothed whales and baleen whales. Toothed whales, such as sperm whales and beaked whales, have asymmetrical skulls and hunt prey using echolocation.
- Baleen whales, including blue whales and humpback whales, have symmetrical skulls and filter large amounts of water to find small critters like krill.
- Having asymmetrical ears allows animals to better decompose complex sounds and precisely recognize a sound’s direction and quality, which is especially useful for hunting in three dimensions. Case in point: the owl, another animal with an asymmetrical skull, which also hunts in 3D spaces.
How the Heck:
- Researchers made their unexpected discovery while looking at fossilized skulls of Basilosaurus, a serpent-like beastie that lived 37 million years ago. The whale’s skull was noticeably asymmetrical, but the scientists thought that this deformation resulted from sediment pressure during fossilization.
- When the researchers tried to “correct” for the deformity using digital models, they saw that the animal’s jaws still didn’t fit together right, leading them to conclude that the skull really was asymmetrical.
- They found the same thing when they looked at the skulls of other ancient whales—”a leftward bend when you look at [the skulls] from the top down,” according to paleontologist Julia Fahlke.
- The researchers suggest that over time, this skull contortion became exaggerated in the toothed whales as they evolved echolocation. The skulls of baleen whales, on the other hand, straightened out, as they don’t require precision hearing to feed.
Image courtesy of Julia Fahlke