Question

Fossil data. In 2001, the discovery of a 47-million-year-old fossil artiodactyl, Rodhocetus kasrani, provided spectacular support for the hypothesis that whales are artiodactyls. This species was clearly related to whales—the fossils have an unusual ear bone found only in whales—and they had a pulley-shaped astragalus. The combination of DNA sequence data and data from the fossil record has clarified how whales evolved. While comparative anatomy and molecular data provide evidence that whales and hippos are closely related, they don’t provide many details on the evolutionary history that connects these groups. The fossil record can help to fill in these gaps.

Q: Whales and hippos (their closest living relative) are very different looking animals! Describe two morphological characteristics, revealed by the fossil record, that help us understand how the ancestors of whales made the transition from land to water

Answer 1

The common feature of both hippo and whales are they possess barely any hair on their bodies and they lack sweat glands which could assist them in aquatic lifw style.

Both hippos and whales evolved from common ancesters called anthracotheres were not large or aquatic. About 15 million years ago, hippos are likely to be evolved from anthracotheres and the first whales evolved over 50 million years ago.

This is supported by the evolved nostrils that is positioned further and further back along the snout from the ancestors. It is the characteristic of living whales called as "blowhole" which is located on top of the head above the eyes.

Reduced pelvis size evolution and separated from the backbone to further increased use of the whole vertebral column.

Skull of the ancestor especially in the ear region surrounded by a bony wall share its similarity with living whales and are unlike those of any other mammal.