Ancient Predators Uncovered

Scientists unearth evidence of tyrannosaurs in North America millions of years before T. rex’s reign

A groundbreaking discovery in New Mexico has reshaped our understanding of the tyrannosaur family tree, introducing a new species that predates the infamous Tyrannosaurus rex. A partial skull of the Tyrannosaurus mcraeensis was discovered and studied by a team of scientists from the New Mexico Museum of Natural History & Science. Mark Loewen PhD’09, a U professor of geology and geophysics and researcher at the Natural History Museum of Utah, was a study co-author. 

The study, published in Scientific Reports, highlights the subtle yet significant differences between T. mcraeensis and T. rex. Unlike its famous cousin, which dominated the landscape approximately 66 million years ago, T. mcraeensis roamed the earth about 72 million years ago, showcasing that the tyrannosaur lineage was established in North America far sooner than paleontologists previously thought.

“The differences are subtle, but that’s typically the case in closely related species. Evolution slowly causes mutations to build up over millions of years, causing species to look subtly different over time,” says Nick Longrich, a co-author from the Milner Centre for Evolution at the University of Bath (UK). 

The new fossils also suggest that larger, more heavily built, and more advanced species evolved in the southern United States, compared to the smaller and more primitive tyrannosaurs that inhabited Montana and Canada. For reasons that remain to be discovered, dinosaurs may have evolved to larger sizes in the south, a body size pattern opposite the pattern seen in modern mammals. 

The newly discovered Tyrannosaurus mcraeensis was roughly as tall and long as a T. rex, which measured up to 40 feet long and 12 feet high. The researchers found that subtle differences in the jaw bones make it unlikely that it was a direct ancestor, raising the possibility that there are still more new tyrannosaur discoveries to be made. 

“As we find more and more specimens, we continue to better understand the evolution of the lineage that led to the largest terrestrial predators ever to roam the earth,” adds Loewen. “This is just the beginning of a series of new tyrannosaur specimens we will unveil in the coming future.”

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