Tyrannosaur hatchlings were chihuahua-sized

Scans of the first known fossils of embryonic tyrannosaurs reveal that they were about the size of a small dog when born. A lower jaw bone and a foot claw, which were found at different sites in western North America, are thought to be from two babies that were 70 and 90 centimetres long. The embryos were not from Tyrannosaurus rex, but an earlier species of related tyrannosaur that has not been identified.