According to a study published in the latest issue of Discovery magazine, scientists at Northeast Medical University in Ohio in the United States found that the largest animal whale on earth was a "miniature deer" that walked on land on four legs 50 million years ago. The team found fossil evidence in Pakistan, making up for previously missing chains of evidence.
A team led by Hans Thewissen reportedly found a 47-million-year-old fossil in Pakistan that featured a muscular, fox-sized animal with an elongated body and tail. The bones stuck in the mud layer reflect the characteristics of modern whales, namely the middle ear space and the bones on the skull structure.
Researchers are finding fossils of "miniature deer".
Scientists have known since Darwin that whales are descendants of mammals that once walked on land, but which mammal it was has remained a mystery. When Tweessen's expedition team discovered the fossil, the missing chain of evidence was compensated for.
Professor Tweessen said the whales were descendants of this ancient "miniature deer" Indohyus.
The researchers confirmed that Indohyus waded through the water like hippos in search of food and used this to avoid predators, which eventually led them to switch from land to a fully aquatic lifestyle.
The researchers reportedly described the fossil skeleton as "a fox-sized mammal that looks like a miniature deer." After a more in-depth analysis, the researchers found similarities between the skulls and ears of Indohyus and whales.
"Miniature deer" Indohyus skeleton restoration.
They determined that indohyus had a thick layer of bone on the outside of the skeleton, much thicker than other mammals of this size. This trait is often found in mammals that wade slowly in the water, such as hippos today.
The aquatic habits of Indohyus are further confirmed by the chemical composition of their teeth, which show oxygen isotope ratios similar to those of aquatic animals, all of which suggest that the creature spends most of its time in water.
The researchers also found that there was a bone in the middle ear space of the fossil skull of this "miniature deer," which is the same as that of modern cetaceans.
In addition, the limb bones of the "miniature deer" are as thick and heavy as those of hippopotamus, suggesting that the animal is a wading animal that uses heavy bones to help stop it from floating.
Indohyus, the "miniature deer," used the water as a mechanism to evade predators, and it wasn't until much later that specific aquatic feeding behaviors developed.
Based on this evidence, the team believes that the whale's ancestors used the water as a mechanism to evade predators, and did not develop specific aquatic eating behaviors until much later.
Whales are said to have their first ancestors between 42 million and 48 million years ago, similar to sea lions. Then there are the Baling whales, about 41 million years ago, including the ancestors of humpback whales and blue whales. This was followed by toothed whales about 7 million years later, which are still cruising in the ocean today.
Text/Nandu reporter Chen Lin