Scientists find missing link in tyrannosaur evolution

(ORDO NEWS) — Paleontologists have discovered the remains of a never-before-seen Daspletosaurus that may have been a direct ancestor of Tyrannosaurus rex. This find could resolve a serious debate about the evolutionary lineage of the most famous dinosaur.

Paleontologists from the University of Montana and the Badlands Dinosaur Museum in North Dakota (both in the United States).

The authors said that during excavations from 2017 to 2021, they discovered a new species of predatory dinosaur, which was named Daspletosaurus wilsoni , in the Judith River Formation in the US state of Montana.

Daspletosaurus belong to a suborder of theropods, which are sometimes called “carnivorous dinosaurs”, although in fact there were also herbivores among them.

There are very few finds of daspletosaurus, the first of them was made in 1921 in the Canadian province of Alberta, but was described in the scientific literature only in the 1970s.

According to modern ideas, they lived in North America in the late Cretaceous period, 75-77 million years ago. The name of these charming creatures can be roughly translated as “terrible lizard.”

Scientists find missing link in tyrannosaur evolution 2
Upper jaw of a new Daspletosaurus

The first Daspletosaurus was named Daspletosaurus torosus , and in 2017 a similar but still quite different Daspletosaurus horneri was found in Montana.

Scientists have suggested that daspletosaurus were the direct ancestors of tyrannosaurs, and even assigned them to the tyrannosaurid family.

At the same time, many researchers disagree on whether tyrannosaurids were a single evolutionary line (where one species is the ancestor of another) or whether these are several closely related species that do not descend from each other.

The lack of a sufficient number of well-preserved fossils only fueled scientific controversy. The authors of the new work believe that they have completed these disputes.

The new species discovered, Daspletosaurus wilsoni , has a unique arrangement of spiky, keratinized growths around the eyes.

It has been identified from fragments of a fossilized skull and skeletal fragments, including a rib and a toe bone, which date back to about 76.5 million years ago.

Researchers believe that D. wilsoni was a descendant of Daspletosaurus torosus and a predecessor of Daspletosaurus horneri.

The anatomy of the newly found animal supports the idea that the Daspletosaurus genus is ancestral to the mighty T-Rex.

All three specimens found to date differ sufficiently from each other to classify them as different species. But at the same time they have a clear generic resemblance.

According to the authors of the work, they all belong to the family Tyrannosauridae , which includes nine genera, including Tyrannosaurus.

Until now, the lineage of tyrannosaurs has been difficult to unravel, making it difficult to pinpoint evolutionary relationships between individual species.

Scientists find missing link in tyrannosaur evolution 3
Skull reconstruction of Daspletosaurus wilsoni

But the discovery of D. wilsoni suggests that the three Daspletosaurus appeared one after the other as “successive ladder rungs in the same evolutionary line” rather than branching off from each other as “evolutionary cousins,” the researchers write.

They considered that D. wilsoni is a transitional species between D. torosus and D. horneri , since it has a number of features in common with older tyrannosaurs: this is the presence of a noticeable set of keratinized growths around the eyes (although these growths are located slightly differently), and also some features of the structure of the skull.

Based on the available samples, it can be assumed that Daspletosaurus looked rather intimidating. They were ten meters long and two and a half meters high at the hips. The length of the skull is at least one meter.

In the mouth of the “terrible lizard” (in the case of D. wilsoni ) more than seven dozen teeth were placed. In addition, these teeth were larger than those of any other predator of that era.

And if we take not absolute numbers, but the size of the teeth relative to the size of the body, then even larger than that of T. rex.

Like the T-Rex, it moved on its hind legs, and its forelimbs were very short, although not as short as those of tyrannosaurs.

Researchers believe that D. wilsoni could prey on both herbivorous and carnivorous contemporaries, as it was the most serious predator of its era.

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