‘Frightening’ never-before-seen tyrannosaurus may be the ‘missing link’ in T. rex evolution
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Paleontologists have discovered the remains of a never-before-seen tyrannosaurus that may have been a direct ancestor of the dinosaur king Tyrannosaurus rex. The newly discovered species could help settle a major debate over T rex‘s evolutionary lineage.
The newly discovered species, Daspletosaurus wilsoni, has a unique arrangement of pointy hornets around his eyes. Tyrannosaurus was identified from parts of a fossilized skull and skeletal fragments, including a rib and toe bone, dating to about 76.5 million years ago during the Cretaceous era (145 million to 66 million years ago). Paleontologists at the Badlands Dinosaur Museum in North Dakota discovered the fossils in the Judith River Formation, in northeastern Montana, between 2017 and 2021, according to a new study, published Nov. 25 in the journal Paleontology and evolution science (opens in new tab).
The team initially stumbled upon the fossils after crew member Jack Wilson noticed a small, flat piece of bone protruding from the bottom of a cliff, which later turned out to be part of the dinosaurnostril. However, excavating the bones proved to be a huge challenge, as they were buried under 8 meters of solid rock. The researchers had to painstakingly chisel away large sections of the cliff with jackhammers before they could even begin excavating the individual bones.
The specimen, designated BDM 107, was playfully nicknamed “Sisyphus” in recognition of the enormous effort required to remove the surrounding rock. (Sisyphus is a figure of Greek mythology who, after cheating death twice, was forced by Hades, the god of death, to repeatedly roll a boulder up a mountain for eternity.)
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That’s what the researchers think D Wilson was the descendant of Daspletosaurus torosus and the predecessor of Daspletosaurus horneri, which probably arose between 77 and 75 million years ago. The anatomy of the newfound beast supports the idea that the Daspletosaurus lineage is the ancestor of the mighty T rex. All three species of daspletosaurs belong to the family Tyrannosauridae, which includes nine genera, including Tyrannosaurus. (The gender Daspletosaurus is Greek for “terrifying lizard”.)
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Until now, the lineage of the Tyrannosauridae has been difficult to unravel, making it difficult to determine the exact evolutionary relationships between individual species.
“Many researchers disagree on whether tyrannosaurids represent a single lineage evolving in situ, or several closely related species that do not descend from each other,” co-authors and paleontologists Elías Warshaw and Denver Fowler wrote in a paper. pronunciation (opens in new tab). This wasn’t helped by a lack of high-quality specimens to research, she added.
But the discovery of D Wilson suggests that the three daspletosaurs came one after the other, as “successive ladder-like steps in a single evolutionary lineage,” rather than splitting off from each other as “evolutionary cousins,” the researchers wrote.
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D Wilson is a good candidate to be a transitional species between D. torosus and D. horneri because it shares some traits with more ancient tyrannosaurs, such as having a prominent set of horns around the eye, as well as traits seen in younger species, such as expanded air sacs in the skull, according to the statement.
“In this way, D Wilson is a ‘halfway point’ or ‘missing link’ between older and younger tyrannosaur species,” the researchers wrote.
Since these species may have evolved one after the other, the team suggests that the rest of the tyrannosaurids, including T rex, could also arise in a similar linear fashion. The researchers are currently planning a new study to explore this idea, according to the statement.
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