The 48-million-year-old skeleton of Indohyus spent much of its life in water and is a close relative of whales. The cell phone is for size comparison.
Credit: NEOUCOM

Finding the Four-Footed Ancestors of Whales
News story originally written on December 20, 2007

Scientists have known for a long time that whales, the largest marine mammals, have distant relatives that lived on land millions of years ago. Little was known about whales’ land-loving ancestors until a team of scientists led by Hans Thewissen of the Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM) started searching for fossil evidence to better understand how whales evolved. In the past 15 years, the research team has identified fossils of extinct whale ancestors that show how over millions of years these mammals evolved from small four-footed land animals to extra-large marine animals.

Now Thewissen and his team have discovered the closest known fossil relative of whales that lived on land. Named Indohyus, this extinct species lived approximately 48 million years ago in what is now the Kashmir region of India. Thewissen's team studied hundreds of fossil bones of Indohyus. They have found similarities between whales and Indohyus in the skull and ear that show their close family relationship.

It may have lived on land, but there is fossil evidence that Indohyus spent much of its time in the water. A fox-sized mammal that looked something like a miniature deer, Indohyus had bones with a thick outside layer, much thicker than in other mammals this size. This characteristic is often seen in mammals that wade slowly in shallow water, such as the hippopotamus today. And the chemical composition of their teeth is similar to aquatic animals.

"The evolution of whales is a tale of the adaptation of a land-based mammal to increasingly aquatic environments," said H. Richard Lane, program director in NSF's Division of Earth Sciences. "This recent discovery provides us with a new understanding of this near-shore-dwelling, shallow-water ancestor."

Last modified December 20, 2007 by Lisa Gardiner.

Shop Windows to the Universe Science Store!

Our online store includes fun classroom activities for you and your students. Issues of NESTA's quarterly journal, The Earth Scientist are also full of classroom activities on different topics in Earth and space science!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

What Is a Fossil?

Fossils are evidence of ancient life preserved in sedimentary rocks. On Earth, they are clues to what living things, ecosystems, and environments were like in the past. The oldest fossils are from mats...more

Triggers of Volcanic Eruptions in Oregon's Mount Hood Investigated

Scientists have learned that Mount Hood, Oregon's tallest mountain, has erupted in the past due to the mixing of two different types of magma. "The data will help give us a better road map to what a future...more

Oldest Earth Mantle Reservoir Discovered

The Earth's mantle is a rocky, solid shell that is between the Earth's crust and the outer core, and makes up about 84 percent of the Earth's volume. The mantle is made up of many distinct portions or...more

It’s Not Your Fault – A Typical Fault, Geologically Speaking, That Is

Some geologic faults that appear strong and stable, slip and slide like weak faults, causing earthquakes. Scientists have been looking at one of these faults in a new way to figure out why. In theory,...more

Lower Solar Activity Linked to Changes in Sun's Conveyor Belt

The sun goes through cycles that last approximately 11 years. These solar cycle include phases with more magnetic activity, sunspots, and solar flares. They also include phases with less activity. The...more

Growth Spurt in Tree Rings Prompts Questions About Climate Change

Studying tree rings doesn't only tell us the age of that tree. Tree rings also show what climate was like for each year of a tree's life, which means they can tell us about climates of the past and about...more

Did Life First Develop in a Mica Sandwich at the Bottom of a Primordial Sea?

Earth's first life form may have developed between the layers of a chunk of mica sitting like a multilayered sandwich in primordial waters, according to a new hypothesis. The mica hypothesis, which was...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF