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I always say this is one of the most convincing palaeontological cases to demonstrate evolution - see Stephen Jay Gould's essay "Hooking Leviathan by Its Past" on it in "Dinosaur in a Haystack" and now they have made more finds linking the fossils with the DNA:
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Fossil study links whales and hippos
Now-vanished cousin was ‘missing link,’ scientists say
Updated: 7:03 p.m. ET Jan. 24, 2005
WASHINGTON - A second look at some 40-million-year-old fossils provides a “missing link” to suggest that the closest living relative of whales is the hippo, a group of scientists said Monday.
Although the hippopotamus does not seem a likely relative of whales, genetic study has suggested they are close. Now, a team at the University of California at Berkeley, the University of Poitiers in France and the University of N’djamena in Chad say they have found more evidence in the fossil record.
“The problem with hippos is, if you look at the general shape of the animal it could be related to horses, as the ancient Greeks thought, or pigs, as modern scientists thought,” researcher Jean-Renaud Boisserie said in a statement.
In Greek the name hippopotamus means “river horse.”
“But cetaceans — whales, porpoises and dolphins — don’t look anything like hippos. There is a 40-million-year gap between fossils of early cetaceans and early hippos,” Boisserie added.
The earliest cetacean fossils date back 53 million years ,while the first hippopotamus fossils date to about 16 million years.
Writing in the Proceedings of the National Academy of Sciences, Boisserie and colleagues propose a new theory that whales and hippos had a common water-loving ancestor that lived 50 million to 60 million years ago.
From it evolved two groups — the early cetaceans, which gradually moved into the water full-time, and a large and diverse group of piglike animals called anthracotheres.
This proposed family tree of modern whales and their first cousin, the hippopotamus, shows how the now-extinct anthracotheres serve as the link between their distant ancestors.
These animals flourished, forming 37 distinct genera across the world before dying out and leaving just one descendant 2.5 million years ago — the hippopotamus.
The theory would class whales, dolphins and porpoises with cloven-hoofed mammals such as cattle, pigs, and camels.
Boisserie argues that some of the older, time-tested ways of classifying animals by body shape and even teeth are not always the most accurate. He and the other researchers based their reinterpretation of the fossil record on molecular findings going back to the mid-1980s, which saw genetic similarities in the blood proteins and DNA of hippos and whales.
Copyright 2005 Reuters Limited.
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