ScienceDaily (Dec. 21, 2007) , 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.
See also: Plants & Animals
Scientists since Darwin have known that whales are mammals whose ancestors walked on land, and in the past 15 years, researchers led by Dr. Thewissen
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 discovered 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.Dr. 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.Dr. Thewissen
and colleagues report key similarities between whales and Indohyus in the skull and ear that show their close family relationship.Thewissen
and colleagues also explored how Indohyus lived, and came up with some surprising results.
According to Dr. Thewissen
, "Clearly, this is not the case, Indohyus is a plant-eater, and already is aquatic.Apparently the dietary shift to hunting animals (as modern whales do) came later than the habitat shift to the water."
Although it may seem strange to think of a tiny, deer-like animal living in water, one modern mousedeer offers something of an analogue to the ancient Indohyus, even though it is not closely related to whales: The African Mousedeer (also called Chevrotain) is known to jump in water when in danger, and move around at the bottom (for a movie showing this go to YouTube and watch ,Eagle vs.Water Chevrotain').
Whale evolution is one of the best documented examples of mammal evolution, and Dr. Thewissen's
discovery adds a significant new piece to the puzzle.
"Not much was known about the earliest whales, until the early nineties," Dr. Thewissen
said."But then, a number of discoveries came in quick succession."
The article documenting Dr. Thewissen's
new discovery, titled Whales originated from Aquatic Artiodactyls in the Eocene of India, was published in the November issue of Nature.
The research by Dr. Thewissen
team was funded by the National Science Foundation
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