[] ''' A small tyrant dinosaur once written off as a teenaged T. rex has now been confirmed as its own species. That animal, called Nanotyrannus, turns out to represent not just one form but two closely related species !
The new study overturns that idea by showing that a nearly complete skeleton had already finished growing.
To see how far these differences went, the team compared more than 200 tyrannosaur fossils from late Cretaceous rocks across North America.
Within that sample, one skeleton once tagged as a teen T. rex instead matched Nanotyrannus and was named N. lethaeus after the river Lethe... []
...and than there is : Stygivenator molnari
Its specific identity can not presently be determined due to its poor preservation making it impossible to rule out an identity as either a specimen of Tyrannosaurus or Nanotyrannus.
