Nanotyrannus ‭(‬Dwarf Tyrant‭)

Nanotyrannus is a controversial genus of tyrannosaurid dinosaur that lived in North America during the Late Cretaceous period, about 68-66 million years ago. It is known from a few fragmentary fossils, including partial skulls and isolated teeth, and was originally described in 1988 by Robert Bakker and colleagues as a separate genus from Tyrannosaurus, based on differences in the shape and number of teeth and other skull features.

However, some scientists argue that Nanotyrannus is not a distinct genus, but rather a juvenile or subadult specimen of Tyrannosaurus. This is because many of the supposed distinguishing characteristics of Nanotyrannus are also found in young T. rex individuals, and some of the Nanotyrannus fossils have been found in rock layers that also contain T. rex fossils.

The debate over whether Nanotyrannus is a valid genus or not is still ongoing among paleontologists, and further study and fossil discoveries may help to resolve the issue.