In fact, as I delved deeper into carnivore cannibalism, I found that the field was rife with controversy – and that the debate included even creatures that hadn’t existed on earth for millions of years. Coelophysis bauri was one of the earliest dinosaurs – a carnivorous and remarkably bird-like biped that lived approximately 200 million years ago across what is now the south-western United States. A fast runner, it stood about three feet tall at the hips and had a body that measured about 10 feet from tip to tail. Equipped with a mouthful of recurved and blade-like teeth, Coelophysis was thought to feed on smaller animals such as lizards.
In 1947 a team from the American Museum of Natural History (AMNH) working at Ghost Ranch in New Mexico unearthed a huge bone bed composed of hundreds of Coelophysis skeletons. After examining the fossils, famed AMNH palaeontologist Edwin Colbert made the dramatic announcement that the abdominal cavities of some of the specimens contained the bones of smaller individuals of the same species. Thus was born the ‘cannibal-Coelophysis hypothesis’ and the subsequent portrayal of Coelophysis and other dinosaurs as cannibals. Reminiscent of the misconceptions concerning black widow spiders, the depiction of dinosaurs as cannibals remained unchallenged for decades.
In 2005, another group of researchers from the AMNH set out to determine whether or not these claims of dinosaur cannibalism could be supported. Led by palaeontologists Sterling Nesbitt and Mark Norell, they performed detailed morphological and histological analyses of the bones. Soon enough, the scientists uncovered a slight problem – not only were the bones in question not from juvenile specimens of Coelophysis, they weren’t even dinosaur bones. Instead, the fragments recovered from the abdominal cavities belonged to crocodylomorphs, a group that includes crocodiles and their extinct relatives, but not dinosaurs.
I interviewed Mark Norell on a beautiful mid-September afternoon at the American Museum of Natural History. His lab is a dinosaur lover’s dream – a remarkable fossil-filled space that opens onto one of the museum’s famous turrets, with a view over a wide swath of Central Park.
“I think there’s very little evidence at all for dinosaur cannibalism,” Norell told me. “Although a lot of it really depends on what you’d call cannibalism. If a tyrannosaur dies and another tyrannosaur comes along and eats it, is that cannibalism? Or is that just scavenging a dead carcass? I have a picture around here someplace of a camel eating a dead camel that was lying there. Is that cannibalism?”
Using the example of besieged cities, where the victims of starvation or exposure were consumed, sometimes by their own relatives, I made the point that hunting and killing aren’t necessarily prerequisites for cannibalism and therefore scavenging your own species would qualify.
But even allowing for a broad definition of cannibalism, in the case of dinosaurs, according to Norell the only compelling evidence appeared to have occurred in the late Cretaceous theropod Majungasaurus crenatissimus, uncovered by geologist Raymond Rogers in a Madagascan rock formation thought to be between 70.6 and 65.5 million years old.
In 2014, I interviewed Rogers to see how he had come to the conclusion that Majungasaurus was a cannibal. He explained that some of the Majungasaurus fossils bore distinctive cut marks. He also noted that there were only a few large carnivores living at the Madagascan site, which they named MAD05-42. One was a crocodile, which would have made no comparable traces on the bones, and the other a small theropod dinosaur, which had tiny teeth. The one remaining suspect was Majungasaurus, which had large teeth – and the denticle patterns matched.
“So there’s no potential that you might be missing another large predator – something you just haven’t dug up yet?” I asked.
“I don’t think we’re missing anything. And if we are missing something it would have to be big, and arguably it would have to be rare. But the bite marks are anything but rare. So… whatever it is, it would have to be really big, really cryptic, really rare, and it would have to bite everything, which doesn’t make any sense.”
“So how do you know that these tooth marks on Majungasaurus bones weren’t made during combat?”