Scientists have determined that Nanotyrannus was a mature, separate species rather than a juvenile Tyrannosaurus rex. A new study analyzed a tiny throat bone from the original fossil, revealing growth patterns indicating adulthood. The findings, published in Science, challenge decades of debate over the dinosaur's identity.
A team led by Christopher Griffin of Princeton University examined the holotype skull of Nanotyrannus lancensis, housed at the Cleveland Museum of Natural History. Discovered in 1942 and initially classified as Gorgosaurus before being renamed in 1988, the skull included a preserved ceratobranchial bone. Bone histology showed maturity patterns, ruling out it being a young T. rex, which grew over 40 feet long compared to Nanotyrannus's estimated 18 feet. Ashley Poust, curator at the University of Nebraska State Museum, stated, 'This small-bodied meat-eater's hyoid bone showed growth patterns that suggest maturity or approaching maturity. This lets us be confident in keeping the name Nanotyrannus.' Griffin added, 'Since this specimen is mature, this definitively shows that Nanotyrannus is distinct from Tyrannosaurus.' The researchers compared the hyoid bone to those from ostriches, alligators, lizards, and other fossils, validating the method for studying dinosaur growth. This follows a recent Nature paper on another potential Nanotyrannus specimen from Montana. The discovery implies multiple large predators coexisted, reshaping views of Late Cretaceous ecosystems. Poust noted, 'You're left with at least two different sized meat eaters in the same environment, which has some big implications for ecology and the extinction of dinosaurs.'