A 74-million-year-old leg bone unearthed from a fossil bed in New Mexico Tyrannosaurus rex suggests groundbreaking insights in a recent study published in Scientific Reports.
This discovery supports the theory that Tyrannosaurus did not migrate from Asia, but instead originated in what is now the American Southwest. This shift in understanding implies that the group evolved into giants much earlier than previously believed.
The shin bone, found in the Kirtland Formation of New Mexico and dating to the late Campanian period, measures 96 centimeters (3.1 feet) long—approximately 84 percent the size of the largest known Tyrannosaurus specimen’s tibia.
Based on its measurements, researchers estimate that the animal weighed around 4,700 kg (10,400 lb), making it the largest known Tyrannosaurus of its time—roughly 50 percent heavier than its contemporary rivals.
The researchers propose three possible origins for the bone: it may belong to a particularly large theropod dinosaur, identified as Vista hebersol; it could represent a newly recognized lineage of giant tyrannosaurs; or it might be an early member of the Tyrannosaurini, related to Tyrannosaurus and its closest relatives.
Of these theories, the authors believe the last is the most plausible. Lead researcher Dr. Nicholas Longrich from the University of Bath noted that the bones closely resemble those of Tyrannosaurus.
“This sounds like Tyrannosaurus,” he remarked in an interview with BBC Science Focus. “If these bones were found in the same beds we know Tyrannosaurus were found, no one would doubt it.”
This suggests that the Tyrannosaurus lineage may have originated in southern North America, with connections to the giant tyrannosaurus, Tyrannosaurus macraiensis, identified from the slightly younger Hall Lake Formation in New Mexico. Longrich discovered this latest bone while photographing specimens on a museum shelf.
Large-scale clustering of Tyrannosaurus remains in the American Southwest indicates that this lineage likely evolved in that area before dispersing across the continent, millions of years prior to their emergence further north.
Further excavations of the Kirtland Formation may help clarify the ownership of this bone. Longrich expressed that “the potential for new materials to be discovered is very high,” noting that teeth might be a promising avenue for discovery due to their superior preservation compared to bones.
A more complete skeleton would allow researchers to formally name the species and determine if it represents a direct ancestor of Tyrannosaurus or an early relative.
Read more:
Source: www.sciencefocus.com
