Nanotyrannus Identified as Separate Species, Not Juvenile T. rex, in Controversial Study

The study, which analyzed growth rings in dinosaur bones, suggests that the Nanotyrannus was a distinct, smaller and more agile species than the T. rex, but some experts remain unconvinced.

New research suggests that the Nanotyrannus, a dinosaur previously thought to be a juvenile T. rex, is actually a separate species.
The study, led by Dr. Nick Longrich and Dr. Evan Saitta, analyzed growth rings in Nanotyrannus bones, showing that the animals were nearly full-size, not fast-growing juveniles.
The researchers also found no evidence of fossils combining features of both the Nanotyrannus and T. rex, supporting the existence of distinct species.
The Nanotyrannus was smaller, had longer arms, and was more lightly-built than the T. rex, suggesting it relied on speed rather than size and strength.
The findings are controversial, with some experts arguing that the study does not settle the question and that the authors do not have a solid grasp on growth variation in tyrannosaurs.

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