Researchers Find Animal That Links Whales to Land
Scientists who study evolution have long known that whales must have had ancestors that lived on land. Some characteristics were dead giveaways, most notably the fact that they are air-breathers.What was still missing was the closest nonwhale ancestor, the animal that was the link to these early whales. Now Dr. Thewissen and colleagues are reporting in Nature that they’ve found the link. It’s Indohyus, a fox-size deerlike animal that lived in what is now India and Pakistan at around the same time as the earliest whales.
The animal, of the order artiodactyla, the even-toed ungulates, has been known for about two decades, but it wasn’t until Dr. Thewissen examined fossils from Kashmir that he realized certain characteristics of the animal’s skeleton tied it to whales. Modern and ancient whales have a bone in their ear that is a half-sphere, thick on the outside and thin on the inside, the better to hear underwater.
“Indohyus has that,” Dr. Thewissen said. “It’s the first nonwhale to have that. That’s the most spectacular piece of evidence.” Further indication of the link to whales was found in the structure of some if its teeth, he said. Other evidence suggests that the animal might have spent at least part of its time in water.
Molecular analysis has suggested that the closest land relatives of whales are members of the hippopotamus family, which are also artiodactyls.
Dr. Thewissen said his work showed hippopotamids might be the modern sister group of whales, but they go back only 15 million years. Indohyus’s age is more in line with early whale evolution. “It’s closer to whales but doesn’t have extant relatives,” he said.
credited to nytimes.com
