For the initial time, scientists have unearthed immediate proof of what a tyrannosaur—often thought of as the epitome of fearsome predators—actually ate.

The fossilized belly contents of 1 member of this dinosaur household ended up described in a new review revealed on Friday in Science Innovations. This exceptional discovery offers insights into the tyrannosaur diet program and the animal’s position in historic ecosystems, both of which have previously only been hypothesized about.

Darren Tanke, a fossil preparator at the Royal Tyrrell Museum of Paleontology in Alberta, identified the specimen in the province’s Dinosaur Provincial Park and delicately taken off it from the rock in which it was encased. He named it “the discovery of his existence,” in accordance to examine co-writer François Therrien, the museum’s curator of dinosaur palaeoecology.

The review examines remnants of two compact oviraptorosaur—feathered dinosaurs with a toothless beak—that ended up found in the belly of a youthful Gorgosaurus libratus, a kind of tyrannosaurid. (The family consists of this species’ more famous cousin Tyrannosaurus rex.) Ahead of the new fossil uncover, researchers could only infer anything about the tyrannosaur eating plan. This kind of inferences have been centered on factors like fossils’ skull and tooth composition, chunk marks on megaherbivores’ fossils and at least a person coprolite, or fossilized feces. Bones uncovered around 1 tyrannosaur fossil have also been interpreted as abdomen contents. The instances that can direct to the fossil preservation of stomach contents are unusual: an animal would will need to die right before the full digestion of prey and then be quickly buried by mud or one more medium.

“Direct evidence of diet program in dinosaurs is frustratingly exceptional,” claims Lindsay Zanno, head of paleontology at the North Carolina Museum of Pure Sciences and an associate analysis professor at North Carolina State College, who was not involved in the new research.

Gorgosaurus lived in the late Cretaceous interval, close to 80 million to 66 million yrs back. Leggy and slender with bladelike enamel in its youth, it produced into a enormous apex predator as an adult, virtually two times the height of a giraffe and weighing as much as an elephant. That transformation produced paleontologists imagine the animal underwent a major dietary shift throughout its lifetime. A youthful Gorgosaurus would not be predicted to assault the megaherbivores it could deal with as an grownup smaller sized prey would make a lot more perception.

Bone advancement assessment revealed that this tyrannosaur was a juvenile concerning five to 7 many years outdated and that the two of its prey had lived for fewer than a year. The differing sum of tummy acid etching on the prey remnants signifies the animals may possibly have been eaten within just hours or times as different meals. And the actuality that the remnants integrated totally articulated legs from two oviraptorosaurs of the identical age, dimension and species indicates the animals had been a favored menu item of this unique tyrannosaur.

The oviraptorosaur legs enabled the staff to detect the prey as Citipes elegans—specimens that have been “extremely rare” in terms of their relatively pristine affliction. “Ironically, the tyrannosaur abdomen in fact guarded the Citipes, enabling it to be preserved—which is rather neat,” states research co-writer Darla Zelenitsky, an affiliate professor at the College of Calgary. These Citipes fossils are, she provides, “the most entire continues to be recognised for that species.”

Gorgosaurus likely “dismembered the little prey, swallowed the legs and still left the rest of the human body out there,” Therrien says. He suggests these legs could have been “the meatiest part” of the animal and miracles, with a snicker, if most likely this Gorgosaurus “didn’t want to be bothered acquiring to cough up some feathers.”

“With the discovery of this remarkable specimen, we have direct, irrefutable proof of not only what this species was snacking on,” Zanno says, “but the gory particulars of how it went about it.”

Oviraptorosaur nests usually contained at the very least 30 or additional eggs. With such huge broods, “you could think about, at sure moments of yr, based on the species and when their breeding season is, this would not be an uncommon prey for predators,” Zelenitsky states. Which is why she isn’t amazed to come across continues to be of this species in this Gorgosaurus’ stomach, specially since she “can’t see the adults going just after these little minor chicken-sized or turkey-sized dinosaurs.”

Zelenitsky speculates that, like birds and crocodiles—closely relevant animals that share a prevalent ancestor with dinosaurs—Gorgosaurus could have had a two-portion belly. The positioning of the two Citipes, she notes, strongly suggests this likelihood, with the legs of the 1st meal exhibiting far more “chemical digestion,” and the legs of the previous food exhibiting far more “mechanical digestion or breakdown.”

This discovery also will help aid what some paleontologists feel is the key to tyrannosaur evolutionary good results: their ability to occupy unique ecological niches during their life span. 1 paleontological secret facilities all-around a putting change in Cretaceous ecosystems. The place at the time there have been a variety of carnivore dimensions and species, by the conclude of the Cretaceous in Asia and North The us, there have been only two forms: substantial tyrannosaurs and much smaller sized dromaeosaurs (feathered theropods this sort of as individuals of the genus Velociraptor)—and “nothing in involving,” Therrien claims.

It has been hypothesized that tyrannosaurs were ready to occupy all of the ecological niches the moment held by former midsize and big carnivores about the program of their development: the tyrannosaurs ate scaled-down prey when they were more youthful and moved on to megaherbivores as adults. Therrien claims they were being likely so thriving as a species simply because “they had developed the capability to occupy all individuals ecological niches all through their have lifespan.”

Zanno, nonetheless, disagrees. “To my intellect,” she states, “shifting prey preference would have been far too popular among the dinosaurian predators to thoroughly make clear these phenomena. The dominance of tyrannosaurs in Late Cretaceous ecosystems is a advanced story we have however to tease apart, but I know for particular it’s a problem we will happily carry on to tackle in the years to arrive.”

1 issue appears to be particular: the discovery of this tyrannosaur gives astounding perception into at the very least a person animal. “[Although] regrettable for the juvenile tyrannosaur,” Zelenitsky claims, “it’s lucky for us that it died when it did just after taking in these meals. Let’s hope extra [will be] located!”