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Hyoid-Bone Study Confirms Nanotyrannus Was Its Own Tyrannosaur Species

By reading growth rings in a throat bone, researchers show the holotype had stopped growing, resolving a decades-long identification question.

Overview

  • Published Dec. 4 in Science, the analysis of the Nanotyrannus holotype’s hyoid indicates the animal was 15–18 years old and skeletally mature.
  • The specimen is the original 1942 Montana skull housed at the Cleveland Museum of Natural History, which lacks limb bones typically used for aging.
  • Researchers validated hyoid histology by matching its growth record to living archosaurs and to a documented Tyrannosaurus rex growth series at the Natural History Museum of Los Angeles County.
  • An independent study released Oct. 30 reached the same conclusion using different bones and anatomical comparisons, reinforcing recognition of Nanotyrannus as distinct from T. rex.
  • The findings imply a smaller, agile tyrannosaur about 5 meters long and roughly 700 kg coexisted with T. rex, reshaping views of predator diversity and potential juvenile–adult niche overlap in Late Cretaceous ecosystems.