New ‘miniature T-Rex’ rewrites the history of the world’s largest predator

A new specimen of one of the most controversial dinosaur species has the potential to overturn decades of research on T. rex.

The “little T. rex” nanoterranes have been the focus of intense debate in paleontology. Scientists have long debated whether Nanoterrans was a separate species or just a young T. rex.

The controversy was sparked in 1999 when the only known fossil of a nanoterranus belonged to a juvenile. More complete fossils since then have failed to produce any definitive answers because they were all too young.

But the debate over the identity of nanoterrains may finally be settled. A new fossil specimen described in the journal The natureis the smoking gun researchers are looking for: an adult nanoterranean.

Known as the dueling dinosaur, this fossil preserves a nearly complete fusion of a nannoteran and a triceratops. They seem to be frozen in battle (whether they were actually fighting when they were buried in the Earth’s sediments remains to be tested).

Although the fossil was discovered in Montana in 2006, it was privately owned until the North Carolina Museum of Natural Sciences purchased it in 2020. Now accessible to scientists, the true nature of this remarkable fossil can be revealed for the first time.

Researchers have confirmed that Nanotyrannus is a separate, miniature type of tyrannosaur, demonstrating that the specimen closely resembles a full-grown adult. The age and maturity of dinosaurs can be estimated by looking inside their bones.

Dinosaurs grow in rapid and slow growth cycles that produce distinct layers of bone. When opened and examined under a microscope, these marks can be counted as rings in a tree.

Using this method, the researchers could determine that Nanoterranus was at least 14 years old when it died, among the oscillating dinosaurs. The researchers also found that its growth rate slowed significantly in its final years, indicating that the individual was close to full body size.

So just how small was this tiny T-Rex? Nanoterrans is only about one-tenth the size of a fully grown T-Rex. Being one of the largest predators to walk the land, however, the T-Rex makes most animals look small. The dueling dinosaur Nanoterranus is more than four meters long and is estimated to have weighed more than 700 kg – as heavy as some of the largest polar bears.

Other specimens of nanoterrans are even larger. A nearly complete skeleton known as Jane, also discovered in Montana in 2001, is estimated to weigh more than a ton, still larger than any land predator today.

Researchers have found enough differences in bone shape in the skulls of the two-legged dinosaur fossils and large genera to separate them into two different species: Nanotyrannus lanceensis and the newly named Nanotyrannus latis.

In addition to small size, another feature that researchers have used to distinguish Nanoterrans from T-Rex is the number of teeth. Despite its very small mouth, Nanoterranus could no doubt pack a powerful bite with its 60-plus teeth. T-rex had 40-50 teeth in its jaws.

The teeth themselves are also different. Nicknamed the “Deadly Banana,” the T-Rex’s teeth are curved and serrated like a steak knife. These unique teeth are perfect for digging into flesh and can crush bone. In contrast, some of the teeth of nanoterrans are straight, chisel-like and without serrations, similar to those of other types of carnivorous dinosaurs.

The T-Rex had famous short arms, which were the source of many jokes and dinosaur expressions. Nanoterranes do not share this feature. Its arms are about the same size as a T-Rex, despite belonging to an animal ten times smaller.

Nanoterrans Stout is overall more lanky than the T. Rex, with its long, muscular body. It has a long touch. The foot bones of the tiny dueling dinosaur Nanoterranus are long enough to be long. The research shows that, although the T-rex couldn’t manage anything faster than a walk, the nanoterranes were well-adapted to run and chase after their prey.

In addition to confirming the existence of this long-controversial dinosaur species, the discovery ends decades of T. rex research. Much of what scientists think about the life and development of T. rex is based on the assumption that many gangly “juvenile” tyrannosaur fossils would have grown into the massive giants known. In light of this discovery, scientists must reassess what life was like for a young T. rex and go back in search of actual juvenile T. rex fossils.

It is widely assumed that T. rex was the only dinosaur of its kind during the last days of the dinosaurs. Some researchers have suggested that the T-Rex was so dominant that other large predators could not keep up with it, including any other medium-sized predators with its own juveniles. This total dominance is now called into question.

T-rex now includes not one but two species of small carnivorous dinosaurs, indicating a more complex and diverse ecosystem that flourished in the Americas toward the end of the dinosaur age.

Despite being arguably the best-known and best-studied dinosaur, T-Rex and its close relatives continue to surprise us from beyond the grave. There is still much to learn about the largest and fiercest predators to ever walk the earth.

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