Ambulocetus

ambulocetus
Ambulocetus (Wikimedia Commons).

Name:

Ambulocetus (Greek for "walking whale"); pronounced AM-byoo-low-SEE-tuss

Habitat:

Shores of the Indian subcontinent

Historical Epoch:

Early Eocene (50 million years ago)

Size and Weight:

About 10 feet long and 500 pounds

Diet:

Fish and crustaceans

Distinguishing Characteristics:

Webbed feet; narrow snout; internal rather than external ears

 

About Ambulocetus

Ambulocetus dates from the early Eocene epoch, about 50 million years ago, when the ancestors of modern whales were literally just dipping their toes into the water: this long, slender, otter-like mammal was built for an amphibious lifestyle, with webbed, padded feet and a narrow, crocodile-like snout. Oddly, an analysis of Ambulocetus' fossilized teeth shows that this "walking whale" thrived in both fresh and salt water lakes, oceans and rivers, a characteristic shared only with a single modern-day crocodile hailing from Australia (and no identified whales or pinnipeds).

Given its slim, unprepossessing appearance--no more than 10 feet long and 500 pounds dripping wet-- how do paleontologists know that Ambulocetus was ancestral to whales? For one thing, the tiny bones in this mammal's inner ears were similar to those of modern cetaceans, as was its ability to swallow underwater (an important adaptation given its fish-eating diet) and its whale-like teeth. That, plus the similarity of Ambulocetus to other identified whale ancestors like Pakicetus and Protocetus, pretty much seals the cetacean deal, though creationists and anti-evolutionists will always continue to doubt the missing link status of this "walking whale," and its kinship to more recent beasts like the truly enormous Leviathan.

One of the odd things about Ambulocetus, and its above-mentioned relatives, is that the fossils of these ancestral whales have been discovered in modern-day Pakistan and India, countries otherwise not well known for their abundance of prehistoric megafauna. On the one hand, it's possible that whales can trace their ultimate ancestry to the Indian subcontinent; on the other, it's also possible that the conditions here were particularly ripe for fossilization and preservation, and early cetaceans had more of a worldwide distribution during the Eocene epoch.