The fossil remains of a 48-million-year-old mammal have been unearthed by a team of scientists working in the Kashmir region of India. The research team, lead by Hans Thewissen of the Northeastern Ohio Universities Colleges of Medicine and Pharmacy, classified the animal as an even-toed ungulate and described it as small and deerlike in build. They named it Indohyus.

Indohyus is thought to be a very special discovery. It appears the animal spent much of its life in or near water. The skull and ear of Indohyus resembles those of whales. Additionally, Indohyus' bones have a thick outer layer characteristic of species that have an aquatic lifestyle. And chemical analysis of Indohyus' teeth show oxygen isotope ratios similar to other aquatic species. Based on these findings, Indohyus may indeed be the land ancestor to modern day whales.

This theory turns popular understanding of whale evolution upside down. Until now, it was a widely held belief that today's whales are the descendents of a terrestrial carnivore—not some deer-sized herbivorous ungulate.

Hans Thewissen and his team of researchers have spent 15 years documenting the evolution of whales. They have identified a series of fossils that show the gradual changes whales underwent. Now their work is grounded in the discovery of a land mammal from which whales may have ultimately evolved.

Find out more:

• Missing Link Between Whales and Four-Footed Ancestors Discovered (NSF)
• Whales Descended from Tiny Deer-like Ancestors (NEOUCOM)
• Thewissen H, et. al. 2007. Whales Originated from Aquatic Artiodactyls in the Eocene Epoch of India. Nature 450: 1190-1194.

Photo courtesy NEOUCOM. Hans Thewissen, Ph.D., Professor of the Department of Anatomy, Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM), holding skull of Indohyus.