Millions of years ago – ages before the Crimson Tide and Auburn Tigers college football rivalry was born – another fight went down in Alabama that has left its mark on history.
According to research published this week in the Journal of Vertebrate Paleontology, a giant fish called Xiphactinus either attacked a plesiosaur or took a bite of the marine reptile after it was dead. Scientists found one of the predatory fish’s huge teeth embedded in the reptile’s long, fossilized neck vertebrae.
Plesiosaurs like the Polycotylus that left behind this fossil in the Mooreville Chalk of Alabama weren’t dinosaurs, but they have long necks that can be reminiscent Apatosaurus (popularized by the character Littlefoot in the movie “The Land Before Time”). Their distinctive form, and marine habitat, have also led to a plesiosaur being the suspected secret identity of the legendary Loch Ness Monster in Scotland.
Though it came from Alabama, the more than 13-foot-long fossil had been tucked away in a specimen drawer at the Field Museum of Natural History in Chicago, Ill., according to the University of Tennessee Knoxville. Professor Christopher Brochu of the University of Iowa Department of Earth and Environmental Sciences noticed the fossil while taking a break from looking at crocodile fossils.
“I sometimes look at other material to see if there’s anything I can show in my classes, and that’s when I saw the bitten vertebra,” he explained.
Brochu brought together a team to identify what mystery attacker tried to snack on the Polycotylus. They used computed tomography (CT) to study the inside of the specimen without damaging it.
“The fossil was virtually dissected by two University of Tennessee undergraduates, Miles Mayhall and Emma Stalker, who built a three-dimensional model of a tooth,” and tracked down an “unexpected culprit,” in the form of an enormous and bony fish.
According to the University of Tennessee Knoxville, the violence of the Xiphactinus’ bite, “partnered with millions of years of burial, fossilization, and eventual excavation, had left the tooth crushed, broken at base and tip, and embedded inside the bone,” linking the fish and the plesiosaur together for millennia. While they were both apex predators, the team wasn’t expecting a fish to be behind the bite.
“We sometimes get these fixed ideas in our heads about who the top predator in any given environment is and who might rest a rung or two down on the food chain,” said lead author and paleontologist Stephanie Drumheller, a teaching associate professor from the Department of Earth, Environmental, and Planetary Sciences at the University of Tennessee. “This fossil is a good reminder that nature is rarely that cut and dry.”
The time when the Xiphactinus bit into the plesiosaur is known as the Cretaceous period. During that time, the oceans of North America “teemed with life” like these giant fish and marine reptiles. With that long neck we mentioned, the plesiosaur might have been at a disadvantage in a fight with a fish.
“Plesiosaurs are famous for their long necks, but those necks come at a price,” said co-author Professor Robin O’Keefe, of the Department of Biological Sciences at Marshall University. “The trachea, esophagus, major arteries and veins, important nerves; all these organs lie vulnerable to attack. A bite to the neck by Xiphactinus would have certainly proved fatal to this animal, if the Polycotylus was not already dead.”
After all this time, it’s not clear what the fish was trying to accomplish, but it seems like the bite was part of a fight rather than trying to score a plesiosaur meal deal.
“It was unlikely that the Xiphactinus, as big as it was, was actually trying to eat the Polycotylus,” said the University of Tennessee Knoxville. “Several famous ‘fish-within-a-fish’ fossils seem to indicate that the predator likes to gulp down smaller fish whole. The embedded tooth could have been the result of the fight instead of a hunt. No matter the original motivation for the bite, its depth and location would have certainly proved fatal.”
This isn’t the first bite-related history to come from Alabama. Per the university, bite marks attributable from other bony fish, sharks, and marine reptiles have been found in the Mooreville Chalk. Together, they indicate the area had a diverse ecosystem of predators that was dangerous even for large species to get out of without a bite mark.
The end of the Cretaceous is “famously marked by a major extinction that killed off all dinosaurs except birds,” according to the National Park Service. That extinction is believed to be due to an impact in the Yucatan.