T. Rex Was Likely an Invasive Species
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An adult T. rex on display at the Dinosaur Discovery Museum in Kenosha, Wisconsin. |
Instead, the giant tyrannosaur was likely an invasive species from Asia that dispersed into western North America once the opportunity presented itself, paleontologists said.
"It's possible that T. rex was an immigrant species from Asia," said study co-researcher Steve Brusatte, a paleontologist at the University of Edinburgh. But he cautioned that the finding isn't necessarily a "slam dunk," and that more research is needed to say for sure. [Gory Guts: See Photos of a T. Rex Autopsy]
T. rex is one of the biggest meat-eaters to ever live on land, but relatively little is known about its family tree. In a study published earlier this month, Brusatte and Thomas Carr, an associate professor of biology at Carthage College in Wisconsin, analyzed 28 different tyrannosaur species and constructed a family tree, noting approximately when and where each species lived.
A family tree showing 28 species in the tyrannosaur family tree, including approximately when and where they lived.
Credit: Stephen Brusatte and Thomas Carr. Scientific Reports. 2016.
Credit: Stephen Brusatte and Thomas Carr. Scientific Reports. 2016.
Fossil evidence is lacking, but researchers suspect that that the predecessors of tyrannosaurs lived on the supercontinent Pangaea, which began to break up about 200 million years ago, during the Triassic period. This would explain why tyrannosaurs are found on different continents,
including Asia, Western North America (called Laramidia at the time),
Eastern North America (Appalachia) and Europe, Carr said.
As time went on, the tyrannosaurs evolved in their respective places, meaning that the tyrannosaurs in Asia grew to look different than the ones in North America. But, around 67 million years ago, the seaway between Asia and North America went down, leaving a land bridge between the two continents, Carr said.
Perhaps T. rex crossed this route into North America, Carr said. Researchers have uncovered countless T. rex fossils in Western North America, but a careful analysis of the species' skeletal features suggests that it is Asian in origin, the paleontologists found.
In fact, T. rex is closely related to two Asian tyrannosaurs, Tarbosaurus and Zhuchengtyrannus, they found.
"Tarbosaurus is the Asian version of T. rex," Brusatte told Live Science in an email. "Or, you could say that T. rex is the North American version of Tarbosaurus. They are so similar in terms of their monstrous size, their proportions, their massive jaw muscles and thick teeth and even many minutiae of their skull bones."
Zhuchengtyrannus is also similar to T. rex, though it's more distantly related, Brusatte and Carr said.
Asian invasion
T. rex lived from about 67 million to 65 million years ago, going extinct when the 6-mile-long (10 kilometer) asteroid slammed into Earth and killed the nonavian dinosaurs.
During that time, the 7-ton (6.3 metric tons) T. rex monster spread from modern-day Alberta to Texas. (A giant seaway in the middle of North America prevented it from reaching the East Coast, the researchers said.) Before T. rex invaded North America, presumably from Asia, other tyrannosaurs lived in Western North America, but they disappeared shortly after T. rex came onto the scene.
It's unclear why these large tyrannosaurs went extinct, but T. rex may have played a role in their demise, the researchers said. [Photos: The Near-Complete Wankel T. Rex]
"Regardless of where T. rex comes from, when it enters the fossil record it seems to take over immediately, like an invasive species," Brusette said. "It rose to the top of the food chain and elbowed out all competitors — or perhaps I should say outmuscled them, as their pathetic little arms didn't have very big elbows."
The new finding is contrary to earlier studies, some of which say that T. rex is the culmination of tens of millions of years of dinosaur evolution within North America, Brusatte said.
"This also is a good example of how different family trees can imply different things about evolution," Brusatte said. "This is why we spend so much time building family trees for fossil groups: They tell us how different species are related to each other, which then allows us to tease out their evolutionary stories, the same way constructing genealogies for our own families tells us how our ancestors led to us."
The study was published online on Feb. 2 in the journal Scientific Reports.
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5D Black Holes Could Break Relativity
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| This artist's concept shows a black hole's surroundings, including its accretion disk, jet and magnetic field. |
Ring-shaped, five-dimensional black holes could break Einstein's theory of general relativity, new research suggests.
There's a catch, of course. These 5D "black rings" don't exist, as far as anyone can tell. Instead, the new theoretical model may point out one reason why we live in a four-dimensional universe: Any other option could be a hot mess.
"Here we may have a first glimpse that four space-time dimensions is a very, very good choice, because otherwise, something pretty bad happens in the universe," said Ulrich Sperhake, a theoretical physicist at the University of Cambridge in England. [8 Ways You Can See Einstein's Theory of Relativity in Real Life]
Doomed from the start
From the beginning, Einstein's theory of general relativity, which describes how matter warps space-time, predicted its own demise. That demise came in the form of singularities, or infinitely curved portions of space-time in which the laws of physics break down, said study co-author Markus Kunesch, an applied mathematics and theoretical physics doctoral candidate at the University of Cambridge.
But in a kind of lucky save, Einstein's theory predicts these singularities exist only behind the event horizons of black holes, from which no matter can escape.
"Even though you have a singularity, it's pretty nicely contained in a high-security lunatic asylum, and it cannot affect anything on the outside," Sperhake, who was not involved in the current study, told Live Science. "This means that general relativity is still perfectly able to explain the entire evolution of the entire universe outside this tiny singularity."
The notion of safely contained singularities, dubbed the cosmic censorship theorem, has held up everywhere in the universe where people have looked.
Naked black holes
But Kunesch and fellow University of Cambridge researchers Pau Figueras and Saran Tunyasuvunakool wanted to probe the limits of the cosmic censorship theorem. They took a look at bizarre proposed black holes that researchers had dreamed up about 15 years ago.
In the past, researchers had proposed a mathematical description of these black rings. However, no one had been able to simulate how they would behave under general relativity. It turned out that, in five dimensions, "naked singularities" would be sitting outside black holes, the team reported in a study published Feb. 18 in the journal Physical Review Letters. That, in turn, would imply that Einstein's theory of relativity would completely break down throughout the universe, not just in black holes.
That doesn't mean Einstein's theory is wrong. Relativity has passed every single test it's faced.
"It is an incredibly amazing theory. It has predicted a lot of new things," Kunesch told Live Science. (Physicists recently discovered one of the last remaining predictions of relativity when they detected gravitational waves formed from the smashup of two black holes 1.3 billion years ago.)
For one, it's extremely unlikely that these relativity-breaking black holes exist. For that to be true, there would have to be extra dimensions. While some theories, such as string theory, do predict the existence of 11 or even 27 extra dimensions, these higher dimensions would be teensy, rolled-up specks — far different from the vanilla, ordinary-size dimensions that we live in, and that black rings were conceived in, Sperhake said. [5 Reasons We May Live in a Multiverse]
The Goldilocks of universes
The findings add to the notion that the universe occupies a sweet spot in terms of its physical properties, Sperhake said. If the gravity had been stronger, our universe would have collapsed soon after the Big Bang. If the gravity had been weaker, no stars could have formed. If the electromagnetism had been slightly different, the chemistry would have gone wonky, Sperhake said. Now, it seems as if the number of dimensions of space-time should be added to the list: If there were any more, the future behavior of the universe couldn't be predicted, at least not by Einstein's theory, he said.
The new results also shine a light in some of the dark, unexplored nooks and crannies of Einstein's groundbreaking theory, Kunesch said.
"It's quite remarkable that, more than 100 years after Einstein's theory was written down, we still don't fully understand what solutions to Einstein's equations look like," Kunesch said. "We still need to establish whether it is completely consistent theoretically. There are still lots of open questions, both on the theoretical level but also on the more experimental level."
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