Whales Descended from Tiny Deer-like Ancestors
Scientists since Darwin have known that whales are mammals whose ancestors walked on land. In the past 10 years, researchers led by Hans Thewissen, Ph.D., Professor of Anatomy, Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM), have identified a series of intermediate fossils documenting whale's dramatic evolutionary transition from land to sea. But one step was missing: The identity of the land ancestors of whales. Now Dr. Thewissen and colleagues announce the discovery of the skeleton of Indohyus, an approximately 48-million-year-old even-toed ungulate from the Kashmir region of India, as the closest known fossil relative of whales. Thewissen's team studied a layer of mudstone with hundreds of bones of Indohyus, a fox-sized mammal that looked something like a miniature deer. Because Indohyus itself is not a whale, but a close cousin, the discovery suggests that the first whales were themselves aquatic, rather than evolving aquatic habits after they took to the water.
Press Release: NEOUCOM Scientist Discovers Missing Link (PDF)
Hans Thewissen, Ph.D., Professor of the Department of Anatomy, Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM), has announced the discovery of the missing link between whales and their four-footed ancestors in the prestigious British Journal Nature.
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Whale Origins Discovery
Presenter(s): Hans Thewissen, Ph.D
Description: Hans Thewissen, Ph.D., Professor of the Department of Anatomy, Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM), talks about the missing link between whales and their land-based ancestors.
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Hans Thewissen, Ph.D., Professor of the Department of Anatomy, Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM), holding skull of Indohyus
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Indohyus Swim by Buell: The 48 million year old ungulate Indohyus from India. Indohyus is a close relative of whales, and the structure of its bones and chemistry of its teeth indicate that it spent much time in water. In this reconstruction, it is seen diving in a stream, much like the modern African Mousedeer does when in danger. Reconstruction by Carl Buell.
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Indohyus by Buell: Reconstruction and close-up of the even-toed ungulate Indohyus. A new discovery of the skeleton of Indohyus indicates that it is a close relative of whales and lived in water.
Reconstruction by Carl Buell.
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Hans Thewissen, Ph.D., Professor of the Department of Anatomy, Northeastern Ohio Universities Colleges of Medicine and Pharmacy and Lisa Noelle Cooper, Doctoral Student, Graduate Program in Biomedical Sciences, Kent State University and NEOUCOM, examining Indohyus skeleton.
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Indohyus skull.
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Indohyus by Dillard: Two individuals of the ungulate Indohyus stand at the water's edge 48 million years ago in India. Indohyus is a close relative of whales, and the structure of the bones and chemistry of its teeth indicate that it spent much time in water.
Reconstruction by Jacqueline Dillard.
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Indohyus Skeleton: Two versions are provided, one with a metric scale, the other with an inch scale. The fossil skeleton of the even-toed artiodactyl Indohyus, which lived 48 million years ago in Kashmir, India. These fossils were found in a layer dense with bones where many skeletons of this species were washed together. Indohyus is a close relative of whales, and lived in water.
Photo by Jeanette Killius, NEOUCOM.
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Indohyus skeleton shown to scale with Razor—style mobile phone.
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Femur cross-section: A cross-section of the femur of the even-toed ungulate Indohyus, which lived 48 million years ago in Kashmir, India. Indohyus is a close relative of whales and lived in water. The thick cortical layer of bone (bright colors in this image taken under polarized light) is typical for mammals that wade, and it serves as ballast to keep them anchored on the streams' floor. The marrow cavity (gray colors) is filled with sediment in this fossil.
Photo by Lisa Noelle Cooper and David A. Waugh.
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