Recent analysis of fossils initially thought to be juvenile T. rex specimens has led researchers to identify them as adults belonging to a distinct species, Nanotyrannus lancensis. This species, first named decades ago but later considered young T. rex, exhibits features such as narrower jaws, longer legs, and more substantial arms compared to the well-known Tyrannosaurus rex.
The research, conducted by Dr. Nick Longrich from the Milner Centre for Evolution at the University of Bath and Dr. Evan Saitta from the University of Chicago, involved a comprehensive re-examination of the fossils, including the study of growth rings, Nanotyrannus anatomy, and the identification of a previously overlooked young T. rex fossil.
Contrary to the previous assumption that these fossils represented juvenile T. rex, the analysis of Nanotyrannus bones’ growth rings indicated that these animals were nearly full size, challenging the notion of fast-growing juveniles. Modeling their growth suggested a maximum size of around 900–1,500 kilograms and five meters, representing about 15% of the size of the larger T. rex.
Importantly, the researchers found no evidence supporting a transitional phase between Nanotyrannus and T. rex in any of the fossils examined. The distinct growth patterns observed in other tyrannosaurs also contradicted the hypothesis of these being young T. rex.
The study’s findings led to the conclusion that Nanotyrannus is a separate species, not closely related to T. rex. It exhibited a more lightweight and long-limbed build, along with larger arms, distinguishing it from its hefty relative. This revelation challenges long-standing debates in paleontology and emphasizes the complexity of distinguishing dinosaur species based on incomplete skeletons.
Dr. Longrich acknowledges the controversy surrounding Nanotyrannus and highlights the ongoing challenge of accurately classifying dinosaurs, suggesting that there might be more to discover about the diversity of these ancient creatures. The study prompts a reconsideration of what researchers thought they knew about one of the most iconic dinosaurs and raises questions about potential misinterpretations in the broader field of paleontology.
Source: University of Bath