10 Terrifying Extinct Cetaceans

Zygophyseter varolai
This predator has been called "killer sperm whale" thanks to its skill at using echolocation to find and rip to shreds its delicious prey. Photo courtesy Notafly/Used under Creative Commons CC BY-SA 3.0 License/Wikimedia Commons

Back in Herman Melville's day, when the whaling industry was at its height, the big prize was spermaceti, a mix of oil and wax found inside the heads of sperm whales. A single whale can have as much as 500 gallons (1,900 litres) of the stuff. There's still some debate about its biological purpose, but the most likely explanation is that it functions as a kind of resonator for echolocation. Modern sperm whales use echolocation to hunt for squid at incredible depths. They send out clicks, and the time interval between when they make the sound and when it bounces back allows them to quickly locate prey in the dark depths of the ocean. And while they have some lower teeth, they don't really use them much.

That's not the case when it comes to one of their Miocene ancestors, which cruised the Mediterranean region roughly 10 million years ago. Paleontologists named it Zygophyseter varolai and gave it the English common name "killer sperm whale" because it was probably very similar to modern killer whales, both in size and feeding habits. The fossil record indicates a fearsome 20-foot-long (6 meters) predator with a well-developed spermaceti organ for echolocating large, powerful prey and ripping them to shreds with big, sharp, deeply rooted teeth [source: Bianucci and Landini]. Z.varolai also had an asymmetrical cranium, which is particularly associated with high-frequency sound production and echolocation. They needed this handy attribute to find and devour those delicious swimmers who emitted high sonic frequencies [source: Fahlke et al.].