An ocean floor in the sand
The Western Desert of Egypt was not always a desert. During the Eocene epoch, between 40 and 36 million years ago, this entire area was a shallow, tropical extension of the ancient Tethys Sea. This former sea floor, now a wind-carved landscape of sandstones and mudstones, is Wadi Al-Hitan. Designated a UNESCO World Heritage Site, the valley contains an enormous concentration of high-quality fossils that record a major shift in life on Earth. Hundreds of marine vertebrate skeletons are found here, including over 400 whales. The sheer number and exceptional preservation of these fossils show a detailed picture of this ancient marine ecosystem.
The most common fossils are two types of early whales, or archaeocetes. The first is the massive Basilosaurus isis, a serpentine predator that could reach up to 21 meters in length. A complete skeleton of an 18-meter-long Basilosaurus has been found at the site. The second is the smaller, dolphin-like Dorudon atrox, which measured about 5 meters long. These creatures were fully aquatic, with streamlined bodies and forelimbs evolved into flippers. Yet, they retained distinct skulls and teeth similar to their land-based carnivorous ancestors. Some Basilosaurus fossils have been found with their last meals preserved, which included smaller whales like Dorudon, as well as crabs and sawfish.