The first known fossils of baby tyrannosaurs reveal that some of the largest predators ever to stalk the Earth started life about the size of a Chihuahua—with a really long tail.
The fossils—a foot claw and a lower jaw—are from tyrannosaurs still in the embryonic stage, when the developing dinosaurs would have been snugly wrapped up in their eggs. Found at different fossil sites in western North America, both date to about 71 to 75 million years ago, when tyrannosaurs had just become the apex predators of their environments.
The itty-bitty claw was uncovered at a site in the Horseshoe Canyon Formation in 2018, within First Nation lands in Alberta. The jaw was also found on indigenous land, in the Two Medicine