Around 74 million years ago, two giant marine reptiles collided in the ancient oceans. Their encounter left behind a remarkable clue — a tooth embedded in the skull of a creature that somehow survived the attack.
The fossil belonged to Mosasaurus missouriensis, a powerful marine reptile that measured approximately 21 feet (6.5 meters) long. It was discovered in 2012 in a shale deposit in southern Alberta, Canada.
At first glance, the skull appeared to tell a familiar story about the violent world of the Cretaceous seas. Mosasaurs were formidable predators known to feed on fish and other marine animals, including smaller members of their own group.
But this fossil revealed something unusual.
Beneath one of the animal’s eyes was a large hole in the bone. Even more astonishingly, a tooth remained lodged inside the injury. The surrounding bone showed signs of healing, suggesting the mosasaur had survived long enough for its body to begin repairing the damage.
Researchers led by Takuya Konishi of the University of Cincinnati analyzed the tooth and concluded that it likely belonged to another mosasaur of a similar size.
That raised a fascinating possibility: this may not have been an attempt to kill and eat its victim.
Instead, the researchers proposed that the encounter could have involved competition between individuals or behavior associated with mating. The attack may have been a confrontation between rivals rather than a predatory hunt.
If that interpretation is correct, the fossil represents rare evidence of a nonfatal attack between mosasaurs.
A single tooth preserved in ancient bone has therefore revealed something remarkable about these prehistoric giants: even among the ocean’s most fearsome predators, not every violent encounter ended in death.