Nanotyrannus lancensis

Gilmore, 1946
Marquage : T. Riedel 1992 5/26. Original : CMNH 7541. MNHN.F.AMN147
Reptilia, Dinosauria, Saurischia, Theropoda, Tyrannosauroidea
Upper Cretaceous, Maastrichtian, 66 million years ago
Hell Creek, Montana Formation, USA

This small tyrannosaurid was found in the same geological levels as the famous T. rex. Even though it displays unique characteristics, such as the number of maxillary teeth, palaeontologists believe that it is in fact a young Tyrannosaurus. Studies of the skeletons of juvenile individuals reveal that at the age of 14 years, Tyrannosaurus had a growth rate of 2 kg per day.

The discovery in Liaoning Province, China, of a primitive tyrannosaurid with feathers suggests that T. rex babies were covered in down.