In a groundbreaking discovery, paleontologists have identified a previously unknown species of tyrannosaur in North America that has been misclassified as a Tyrannosaurus rex for decades. The newfound sister species, named Tyrannosaurus mcraeensis, is believed to be the closest relative of T. rex and may even surpass the dinosaur king in size, according to a recent study.

The story began in 1983 when paleontologists uncovered a partially fossilized tyrannosaur skull in the Hall Lake Formation of New Mexico. The fossil, initially identified as a T. rex skull, has been on display at the New Mexico Museum of Natural History and Science (NMMNHS) ever since. However, in 2013, a team of researchers decided to reevaluate the skull due to subtle irregularities in its shape.

Published in the journal Scientific Reports on January 11th, the study revealed that the skull dates back to the Cretaceous period, between 73 million and 71 million years ago. This makes T. mcraeensis approximately 3 million to 5 million years older than T. rex.

Besides the age difference, distinct morphological features differentiate T. mcraeensis from its famous relative. The most noticeable dissimilarity is the slender and curved shape of the lower jaw, lacking the prominent hornlets found above the eyes in T. rex. Moreover, T. mcraeensis possesses fewer teeth, a characteristic it shares with its cousin T. rex.

The size of the fossilized skull suggests that this particular T. mcraeensis specimen was similar in size to an average adult T. rex, which reached lengths of approximately 39 feet (12 meters). However, the researchers believe other individuals of the species could have been even larger.

Study co-author Nick Longrich, a paleontologist at the University of Bath in the U.K., stated that T. mcraeensis likely occupied the apex predator position in its time, just like T. rex. Longrich further suggested that if the two species had coexisted, they would have been evenly matched in combat.

Prior to this discovery, T. rex's closest relatives were Tarbosaurus bataar and Zhuchengtyrannus magnus, both found in China and Mongolia. These species predate T. rex, indicating a possible Asian origin for tyrannosaurs. However, the newfound tyrannosaur's presence in North America suggests that the continent, specifically the landmass known as Laramidia, may have been the more likely birthplace of the tyrannosaur lineage, with subsequent migration to Asia.

The findings highlight the importance of New Mexico as a hotspot for dinosaur discoveries. Co-author Spencer Lucas, the curator of geology and paleontology at NMMNHS, emphasized that there are still numerous undiscovered dinosaur species awaiting exploration in the state, both in the rocks and within museum collections. The recent identification of T. mcraeensis further solidifies New Mexico's reputation as one of the world's premier destinations for paleontological research.

As the mysteries of the tyrannosaur family continue to unfold, this groundbreaking discovery reshapes our understanding of North American dinosaur evolution and underscores the ongoing quest to unearth the secrets of Earth's ancient past.