Paleontologists have identified the first known fossils of hatchling Tyrannosaurus rex, a discovery made while examining museum collections. The rare fossil, found in Canada, confirms that these predators were small—roughly the size of a house cat—and were active hunters immediately after leaving the nest.
A Hidden Discovery in the Royal Saskatchewan Museum
The identification of the fossil resulted from a careful review of small dinosaur bones that had been previously misidentified or tucked away in storage. Nicholas Longrich, a paleontologist and evolutionary biologist at the University of Bath, discovered the specimen among fossils housed at the T. rex Discovery Centre of the Royal Saskatchewan Museum in Canada. The bone, a third metatarsal, initially defied classification.
Longrich noted that the bone did not fit into existing categories for known theropod dinosaurs. Upon closer inspection, the porous texture of the specimen indicated it belonged to an immature animal. By process of elimination, researchers concluded it was a very, very tiny T. rex,
marking it as the smallest T. rex that we’ve ever seen.
Anatomy and Behavior of Hatchling Tyrannosaurs
To better understand the life of the hatchling, Longrich collaborated with Eric Snively, a professor of anatomy and cell biology at the Oklahoma State University Center for Health Sciences. Utilizing high-tech CT scanning, the team examined the internal structure of the fossil. The scans revealed an absence of growth rings, confirming the animal was less than a year old at the time of its death.
The imaging also displayed a high concentration of interconnected blood vessels and bone cell spaces, evidence that the creature was in a phase of rapid development. According to reporting from Oklahoma State University, these features indicate that the hatchling weighed approximately five pounds. The researchers corroborated these findings with T. rex hatchling teeth, which showed signs of heavy wear, suggesting the young dinosaurs were already consuming bone.
“The babies were smashing into the bones of their food, just like giant adults,”
Eric Snively, Oklahoma State University Center for Health Sciences
Snively added that Tyrannosaurus were unsafe at any size and that babies were quickly out of the nest and killing the heck out of things.
Reproductive Strategies and Evolutionary Insights
The findings, published in the journal Biology, provide a clearer picture of how Tyrannosaurus rex managed its population. Analysis of the fossil suggests that these dinosaurs likely laid large clutches of eggs, perhaps numbering between 15 and 30 at a time, with some estimates suggesting between 50 and 100 eggs in a clutch also possible. This high-volume reproductive strategy implies a limited level of parental care compared to modern birds, though researchers believe some nest-guarding likely occurred.
As Fox Weather reported, the discovery challenges previous gaps in the timeline of dinosaur development. The evidence indicates that, much like crocodiles or modern ground birds, hatchlings were independent and mobile shortly after emerging from their shells. This survival strategy allowed the juveniles to occupy their own niche as predators within the ecosystem, growing into the massive bone-crushing adults.
The research underscores the value of revisiting long-held museum collections. By applying modern imaging techniques to fossils that have been on shelves for years, scientists are uncovering new data about the life cycle of one of history’s most famous dinosaurs. Future research will likely continue to focus on these early life stages to better map how Tyrannosaurus rex maintained its role as a predator throughout its lifespan.
