Massive Tyrannosaur Shin Bone Discovered in New Mexico

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Archaeologists working in the Kirtland Formation fossil site in New Mexico's San Juan Basin have uncovered a massive tyrannosaur shin bone, or tibia, that measures nearly 38 inches long and 5 inches in diameter. The bone is over three-quarters the size of the equivalent bone from one of the largest known T. rex specimens, suggesting the existence of a previously unknown giant tyrannosaur species that roamed the Earth around 74 million years ago during the Late Campanian age.

Why it matters

This discovery challenges existing understandings of the evolution and diversity of tyrannosaurs, a group of meat-eating dinosaurs that eventually gave rise to the iconic Tyrannosaurus rex. The massive size of this shin bone indicates the presence of an even larger tyrannosaur predator that lived millions of years before T. rex, providing new insights into the prehistoric ecosystem.

The details

The ancient bone was found in the Kirtland Formation, a fossil-rich site in New Mexico's San Juan Basin. Researchers suspect the bone belonged to a tyrannosaur, a broad group of carnivorous dinosaurs that emerged around 170 million years ago. While tyrannosaurs eventually evolved into massive predators like T. rex, this newly discovered specimen suggests some earlier tyrannosaurs may have been much larger than previously thought. The shin bone's location in the rock layers dates it to around 74 million years ago, during the Late Campanian age.

• The newly uncovered shin bone, or tibia, dates back approximately 74 million years to the Late Campanian age.