T. Rex hatchlings were cat-sized but already deadly

New research reveals that baby Tyrannosaurus rex were about the size of a house cat when they hatched, but already possessed sharp teeth and a powerful bite. The study, published in the Journal of Vertebrate Paleontology, analyzed a fossilized jawbone from a juvenile T. rex that lived around 66 million years ago in what is now Montana. The specimen, which is about three inches long, indicates that the hatchling was roughly two to three feet in length and weighed around five to ten pounds. This finding matters because it provides the first concrete evidence of the size of T. rex at birth, filling a gap in the dinosaur's life history. Previously, scientists had only estimates based on egg sizes and growth rates. The study also shows that even at this tiny size, the baby T. rex had serrated teeth and a strong bite force, suggesting it was capable of hunting small prey from the start. The researchers used CT scans to examine the jawbone's internal structure and growth lines, which allowed them to determine the animal's age and size at hatching. The next step for scientists is to search for more fossils of very young T. rex to better understand their early development and behavior. This discovery also raises questions about how such small hatchlings survived in a world dominated by large predators.