New fossils show whales related to hippos, cows

New fossil discoveries add weight to the conclusion that whales are related to land-based plant-eaters such as cows and hippopotamuses rather than to an extinct group of carnivores, two groups of researchers report.

Scientists have known that whales evolved from four-legged land animals million of years ago. However, which branch of the animal kingdom whales split from has been a matter of debate.

Immunological tests in the 1950s and recent DNA tests have shown a relationship to plant-eating artiodactyls -- hoofed mammals having an even number of toes, such as pigs, cows and hippopotamuses.

Earlier, those test findings had had not been supported by fossil evidence, which pointed more to a link to carnivores. Now, authors of two new studies say their fossil finds, in separate areas of Pakistan, have convinced them that the tests are correct.

"With this find, it's clear that I and all my colleague were barking up the wrong tree," said Hans Thewissen of the Northeastern Ohio Universities College of Medicine in Rootstown, Ohio.

Thewissen, who discovered remains of two species of four-legged, 50 million-year-old whale ancestors, is the lead author of a paper that appeared in the journal Nature.

Thewissen compiled the skeletons from bones found in a bed of fossils in the Punjab area of northeast Pakistan.

Philip Gingerich, a professor of geology and paleontology at the University of Michigan and the lead author of a paper appearing in the journal Science, said his group found two skeletons of two other separate species, about 47 million years old, in the Balochistan area of southwest Pakistan. One skeleton was almost complete, he said.