First baby T. rex fossils found in museum drawers

Paleontologists have identified the first known fossils of Tyrannosaurus rex hatchlings, revealing that the most famous predator in Earth's history started life as a scrappy, cat-sized creature weighing about as much as a Yorkshire terrier — and was already biting into bone from the start.

A "Vanishingly Rare" Find Hidden in Museum Drawers

The discovery, published in the peer-reviewed journal Biology, came not from a dramatic dig site but from museum storeroom drawers, where tiny, overlooked bones had been gathering dust for years. Nick Longrich, a paleontologist and evolutionary biologist at the University of Bath, led the research alongside Eric Snively of Oklahoma State University and other colleagues.nypost+2

"Going through museum collections, my colleagues and I have discovered the first remains of hatchling tyrannosaurs," Longrich said. One specimen, a third metatarsal — a middle foot bone — initially appeared to belong to a small adult dinosaur. But its extremely porous surface, a hallmark of rapid bone growth in immature animals, told a different story. When compared against other species of its era, only one fit: T. rex.sciencealert

Smaller Than Scientists Thought

The team estimates the main specimen was about 75 centimeters (30 inches) long and weighed roughly 2.5 kilograms (5.5 pounds), with newly hatched individuals potentially as light as 1.7 kilograms. That is considerably smaller than previous estimates, which had suggested tyrannosaur hatchlings could have measured up to a meter from snout to tail.nypost+1

The teeth showed wear marks, indicating the babies were already crunching bone. "The teeth were chunky and worn, so the babies were biting into bone just like a 10-ton adult sundering bones of a big Triceratops," Snively told ScienceAlert.sciencealert

From these revised size estimates, the researchers calculated that tyrannosaur eggs were smaller than previously assumed, meaning females likely laid far more of them — an estimated 20 to 30 per clutch.sciencealert

Rethinking Dinosaur Parenting

The findings challenge a long-held assumption that T. rex, like modern birds, invested heavily in raising a small number of young. Instead, the small, precocial hatchlings and large clutch sizes suggest tyrannosaurs leaned more toward a strategy of producing many offspring and leaving them largely to fend for themselves.semanticscholar+1

"It shows tyrannosaurs are transitional between reptiles like crocodilians and turtles on the one hand, and modern birds on the other," Longrich said. "Avian-mammal intensive parental investment and care seems to evolve gradually in the Mesozoic."sciencealert