Basilosaurus the Bone-Crusher

Bite force is all the rage lately. This year alone paleontologists have published new bite force estimates for the largest rodent of all time and a prehistoric crocodylian heavyweight. And in the pages of PLOS ONE, Eric Snively, Julia Fahlke, and Robert Welsh have brought another superlative chomper to attention – the early whale Basilosaurus.

The inspiration for the study came from damaged bones. In 2012 Fahlke published a paper on a set of busted whale skulls from the 38-36 million year old strata of Egypt. Each of the four were from juveniles of a whale called Dorudon – a sinuous, fully-aquatic whale that still had differentiated teeth for gripping and shearing – and they all bore bite marks that matched the size and spacing of teeth belonging to the similar, but much larger, Basilosaurus. The bigger whales were grabbing the young Dorudon by the skulls, sometimes repositioning their prey before a final crunch.

The ancient toothmarks offered compelling evidence that, much like today’s orcas, Basilosaurus was a whale that ate other whales. But as a check on its biting power, Snively, Fahlke, and Welsh turned to an engineering technique called finite element analysis to run Basilosaurus through some virtual chomping.

Working from a skull belonging to a beautifully-complete specimen of Basilosaurus isis found in Egypt, the researchers found that the whale could bite with a force of over 3,600 pounds at the position of its upper third premolar. As suggested by Fahlke, this was the part of the mouth Basilosaurus used to crack open little Dorudon skulls and the estimated force is more than sufficient to penetrate through skin, muscle, and bone. And while the figure is undoubtedly influenced by the size of Basilosaurus, as Andy Farke points out, this is still the highest bite force yet estimated for a mammal.

Basilosaurus didn’t go right for a killing stroke, though. Some of the Dorudon skulls hint at initial capture with the conical, canine-like teeth at the front of the jaw first, and the researchers found that Basilosaurus could grip victims with over 2,300 pounds of force. With prey in place, Basilosaurus could then toss it back further along the jaw for a deadly shear bite. Crocodylians sometimes do the same with turtles and other hard-shelled prey, nabbing them with pointed teeth before obliterating their victims’ defenses with a back-tooth bite.

All that biting power allowed Basilosaurus to effectively dismantle large prey. The skulls of dead Dorudon and Basilosaurus teeth worn from scraping against bone attest to that grisly fact. And as Snively, Fahlke, and Welsh note, that Basilosaurus was capable of such shattering bites also fits with the picture of the whale as a consummate hunter.

The highest bite forces known – whether recorded from live animals or estimated from bones – belong to active predators, including carnivores like saltwater crocodiles, spotted hyenas, great white sharks, and Tyrannosaurus. Sure, powerful bites might let them take advantage of carrion from time to time, but the ability to deliver devastating chomps is also a critical skill for predators who must quickly disable their victims. What was true for spotted hyenas was likely true for Basilosaurus, making the ancient mammal one of the most frightening whales of all time.

Reference:

Fahlke, J. 2012. Bite marks revisited – evidence for middle-to-late Eocene Basilosaurus isis predation on Dorudon atrox (both Cetacea, Basilosauridae). Palaeontologia Electronica. 16 (2), 1-16.

Snively, E., Fahlke, J., Welsh, R. 2015. Bone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the Late Eocene of Egypt estimated by finite element analysisBone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the Late Eocene of Egypt estimated by finite element analysisBone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the Late Eocene of Egypt estimated by finite element analysis. PLOS ONE. doi: 10.1371/journal.pone.0118380