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Paleontologists have examined an exceptionally well-preserved, near somatically mature tyrannosaur skeleton from the Hell Creek Formation of Montana. Their results show that the specimen shares features with the holotype specimen of Nanotyrantand demonstrate that this lineage is distinguishable from Tyrannosaurus.A pack of Nanotyrant brazenly attacks a juvenile Tyrannosaurus rex. Image credit: Anthony Hutchings.“This fossil flips decades of Tyrannosaurus rex research on its head,” said Dr. Lindsay Zanno, a researcher at North Carolina State University and the North Carolina Museum of Natural Sciences. Using growth rings, spinal fusion data and developmental anatomy, the researchers demonstrated that the new specimen was around 20 years old and physically mature. Its skeletal features — including larger forelimbs, more teeth, fewer tail vertebrae, and distinct skull nerve patterns — are features fixed early in development and biologically incompatible with Tyrannosaurus rex. “For Nanotyrant...