Washington: A team of scientists has rediscovered a 17 million year old fossil of a beaked whale once native to East Africa.
The fossil, which was original unearthed in 1964, but lost for nearly half a century after the skull was misplaced, is the oldest known fossil of a beaked whale and strongly suggests an exact time for when the East African plateau was once turned into a savannah.
The fossil, which is from the beaked Ziphiidae whale family, was discovered 740 kilometers inland at an elevation of 620 meters in modern Kenya's harsh desert region, said co-author Louis L. Jacobs, Southern Methodist University, Dallas.
At the time the whale was alive, it would have been swimming far inland up a river with a low gradient ranging from 24 to 37 meters over more than 600 to 900 kilometers, said Jacobs.
The whale was stranded up river at a time when east Africa was at sea level and was covered with forest and jungle, added Jacobs. As that part of the continent rose up, that caused the climate to become drier and drier. So over millions of years, forest gave way to grasslands. Primates evolved to adapt to grasslands and dry country and that's when, in human evolution, the primates started to walk upright.
Identified as a Turkana ziphiid, the whale would have lived in the open ocean, like its modern beaked cousins. Ziphiids, still one of the ocean's top predators, are the deepest diving air-breathing mammals alive, plunging to nearly 10,000 feet to feed, primarily on squid.
In contrast to most whale fossils, which have been discovered in marine rocks, Kenya's beached whale was found in river deposits, known as fluvial sediments, said Jacobs. The ancient large Anza River flowed in a southeastward direction to the Indian Ocean. The whale, probably disoriented, swam into the river and could not change its course, continuing well inland.
Jacobs noted that usually whales aren't found so far inland, many of the known beaked whale fossils are dredged by fishermen from the bottom of the sea. Determining ancient land elevation is very difficult, but the whale provides one near sea level.
The study is published in the Proceedings of the National Academy of Sciences.