Researchers have made a significant breakthrough regarding a dinosaur unearthed in the 1940s, resolving a long-standing debate about its origins. This discovery, detailed in a recent study, identifies the dinosaur not as a juvenile Tyrannosaurus rex but as a separate species altogether.
Initially, scientists only had a skull to examine, which made it challenging to determine whether it belonged to a young or adult dinosaur. The debate intensified with the addition of another specimen known as “Jane,” but clarity remained elusive. The pivotal evidence comes from a complete skeleton found in Montana in 2006, which has now been classified as a distinct species.
According to Lindsay Zanno, a co-author of the study from the North Carolina Museum of Natural Sciences and North Carolina State University, this finding “rewrites decades of research on Earth”s most famous predator.” The skeletal remains revealed growth rings in the bones, indicating that the dinosaur was an adult and approximately half the size of a fully-grown T. rex.
Through comparisons of growth patterns with other reptiles, such as crocodiles, researchers concluded that the significant differences found in the skull structure, nerve patterns, and sinuses of this dinosaur suggest it could not merely be a juvenile T. rex undergoing puberty. The team identified the creature as Nanotyrannus lancensis, a close relative of T. rex that is believed to have been a nimble predator.
This new species is characterized as a small-bodied predator designed for speed, featuring long, powerful arms that are proportionally larger than those of T. rex, as noted by Zanno. Fellow paleontologist Holly Woodward from Oklahoma State University, although not involved in the study, acknowledged the increasing support for the existence of this relative of T. rex but remains skeptical about classifying other specimens like Jane as new species.
However, the debate is not entirely settled. Thomas Carr, a vertebrate paleontologist at Carthage College, pointed out that while the new skeleton is confirmed as an adult, it might represent a sister species to T. rex rather than a distant cousin. He emphasized that the skull shape similarities between T. rex and the unidentified specimens prevent him from fully endorsing this new classification.
James Napoli, another co-author from Stony Brook University, highlighted that clarifying this case of mistaken identity is crucial for understanding the growth patterns of T. rex. The implications of this discovery extend to the broader ecological landscape of the late Cretaceous period, raising questions about whether T. rex was the dominant predator or if smaller, agile predators like Nanotyrannus also played significant roles.
The skeleton, nicknamed “Dueling Dinosaurs,” was discovered intertwined with the bones of a Triceratops and is currently displayed at the North Carolina Museum of Natural Sciences. This study emerges alongside recent findings suggesting that dinosaur populations were still thriving in North America just prior to the asteroid impact. Researchers analyzed a section of the Kirtland Formation in northern New Mexico, known for its diverse dinosaur fossils, contributing to our understanding of dinosaur evolution.
In June, scientists announced the identification of a smaller-bodied ancestor of T. rex from the plains of Mongolia, named Khankhuuluu mongoliensis, indicating that apex predators like T. rex evolved from these smaller tyrannosauroids.
