A beautiful artistic reconstruction of Indohyus by Carl Buell.

During the last 30 years paleontologists have uncovered a startling amount of fossil evidence which has illuminated the early evolution of whales. The earliest members of the cetacea looked nothing like the marine mammals we are familiar with today, and in December of 2007 a paper in Nature identified a small hoofed mammal called Indohyus as one of the closest relatives to the earliest whales. This hypothesis was supported by a subsequent study published a few months ago in the same journal.

One of the most interesting aspects of Indohyus was that parts of its skeleton were thickened through osteosclerosis. The earliest whales, the archaeocetes, exhibited this