Researchers studying the bite marks left behind on a fractured fossil skull have calculated the incredible bone-crushing bite of an ancient whale: Basilosaurus isis chomped down on other whales with the force of over 1,600 kilograms (3,500 pounds). The findings were published in PLOS ONE this week.
Modern whales emerged from archaeocete whales in the latest Eocene or earliest Oligocene around 34 million years ago. But unlike their early ancestors, today’s whales don’t chew. Baleen whales filter feed, while toothed whales capture prey and swallow them whole (or at least in large pieces). The archaeocete Basilosaurus isis lived during the late Eocene between 40 million and 34 million years ago. Its name sounds like a dinosaur's because when Basilosaurus fossils were first described in the early 19th Century, PLOS blogs explains, its backbone resembled those of prehistoric marine reptiles. Its tooth wear suggests that it crushed large, hard objects like mammal bones—in addition to feeding on fish, based on fossilized stomach contents. By matching their teeth to bite marks on the skulls of juvenile Dorudon atrox whales, researchers previously revealed that Basilosaurus ate other whales.
Now, a trio led by Eric Snively from the University of Wisconsin—La Crosse examined a near-complete skeleton of an adult Basilosaurus isis excavated decades ago from Birket Qarun Formation of Wadi Al-Hitan in Egypt. It had a total body length of 16 meters (52 feet), and its skull alone was over a meter long.
The team modeled its bite force by combining two techniques: the dry-skull method estimates muscle force and Finite Element Analysis looks at reaction forces at the teeth and jaw joint. And since Basilosaurus tooth wear and bite marks on Dorudon atrox fossils indicate preferential bite positions, the team was able to localize estimates of bite force to functionally critical locations.
According to their model, at its upper third premolar, Basilosaurus packed 16,400 Newtons of force—and possibly more. Basilosaurus bit Dorudon calves across the head, and sometimes adjusted the prey in its mouth before delivering the bone-penetrating bite. Additionally, comparisons with carnivores and scavengers suggests Basilosaurus was an active predator.
Their bite force estimates for Basilosaurus are the largest known for any mammal—much more than today’s bone-breakers, like the spotted hyena. Captive hyenas exert about 3,500 N, and wild hyenas in Africa likely exert double that. Crocodylians and tyrannosaurs, however, have bite forces well beyond that of Basilosaurus.