Topping out at a length of about 8 meters (26 ft), the killer whale (or orca) is the ocean's top predator – it even goes after other kinds of whales. With that in mind, just imagine what fun a 15-meter (49-ft) predatory whale would be. That's the approximate skeletal length of Basilosaurus isis, a prehistoric toothed whale that is now believed to have likewise fed on its fellow whales.
In 2010, scientists from Germany's Berlin Museum für Naturkunde (Museum of Natural History) unearthed a fossilized Basilosaurus isis skeleton in Cairo. The skeleton was disarticulated, suggesting that currents and/or scavengers had pulled the bones apart from one another. It dated from late in the Eocene Epoch – that entire epoch lasted from 56 to 33.9 million years ago.
Also present at the site were broken bones from various bony fish, and from a smaller species of whale known as Dorudon atrox (the skeletons of B. isis and D. atrox are pictured below). The majority of these bones were found clustered within the belly cavity area of the B. isis, suggesting that it had eaten the other animals.
It had been hypothesized that the D. atrox whales may have simply been scavenging the B. isis carcass, and then died at the site. A new study, however, points out the fact that they were all juveniles which would only have been feeding on their mother's milk at the time. Additionally, some of their skulls displayed bite marks – predators typically target the heads of their prey.
The scientists now believe that Cairo's Wadi Al Hitan ("Valley of Whales") area was once a Dorudon atrox calving site, and thus also a hunting ground for Basilosaurus isis.
A paper on the research, which was led by the museum's Manja Voss, was recently published in the journal PLOS ONE.
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