The Tyrannosaurus rex, probably the most famous of all dinosaurs, still fascinates palaeontologists to this day and continues to pose mysteries. This colossus with its enormous jaws moved on two legs, stretched to around twelve metres in length and weighed an impressive ten tonnes. Its existence coincided with the final stage of the Cretaceous period, a comparatively short period that ended around 66 million years ago, when most dinosaurs became extinct. Due to the lack of close relatives of T. rex, questions about its origin and distribution area have remained unanswered until now. However, researchers have now attempted to unravel these mysteries.
T. mcraeensis not a direct ancestor of T. rex, but an uncle
The evolutionary lineage of the Tyrannosaurini, to which only T. rex belongs, was previously unknown, as close relatives of this giant were missing. While the “king of the tyrant lizards” inhabited North America, the most similar dinosaurs to date have been found in what is now Mongolia in Asia. Although many details such as scaly lips and locomotion have been researched, important questions about this predatory dinosaur remain unanswered.
The researchers, led by Nicholas Longrich from the University of Bath, have analysed a partially preserved skull of a dinosaur in the Hall Lake Formation in the southwest of the US state of New Mexico. Originally, this skull was thought to be a T. rex. The researchers are now one step closer to clarifying the origin of the T. rex. A find in the south of the USA, which was labelled Tyrannosaurus mcraeensis, appears to be the closest relative of T. rex, as the team reports in the journal Scientific Reports.
The research team argues that this find is a separate species, in particular due to new dating, which dates the age of the find layer back to 71 to 73 million years. These dinosaurs thus lived several million years earlier than previously known T. rex specimens. However, T. mcraeensis was not a direct ancestor of T. rex, but basically an uncle. The group writes that at least two giant Tyrannosauridae existed simultaneously in North America, with the other species ultimately leading to T. rex.
These enormous predatory dinosaurs developed their impressive size in a relatively limited area until around 72 million years ago, towards the end of the so-called Campanian period. Only later did they spread northwards. Researchers speculate that the giant predatory dinosaurs evolved in the south of Laramidia, a region that stretched from Alaska to Mexico and formed the western part of North America at the time. This region was separated from the eastern part of the continent, Appalachia, by a shallow sea, which later retreated.
The unprecedented size of these predatory dinosaurs could possibly be due to the fact that they were able to prey on the giant herbivores that existed at the time, such as Alamosaurus or Magnapaulia.
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