Spinosaurus didn't swim after its dinner, study claims

Spinosaurus was one of the largest carnivorous dinosaurs and it ate fish. That much paleontologists agree.

But did it wade into the rivers and pluck them from the water like a grizzly bear? Or did it dive after its prey like a penguin or sea lion?

This has caused great controversy among dinosaur experts.

One group is increasingly convinced that Spinosaurus was rare among dinosaurs: it swam beneath the surface with its head stuck underwater. Others say no way.

The latest salvoPublished Wednesday in the journal PLOS One, it comes from the Spinosaurus-can't-swim team to counter a pro-swimming article published a few years ago. Previous work published in the journal Nature, In general, animals that spend a lot of time in the water, such as penguins, have dense bones that provide stability and make it easier to dive. The Nature paper concluded that Spinosaurus also had dense bones and was therefore most likely a swimmer.

But that bone density analysis is “statistically ridiculous,” said Nathan Myhrwaldt, a former Microsoft chief technology officer and amateur paleontologist who led the new research with University of Chicago paleontologist Paul Sereno.

Dr. Myhrvold and Dr. Sereno also argued that Spinosaurus's awkward body shape would have made it a poor swimmer, had it been able to swim. Dr Myhrvold said the dinosaur's weight distribution would have made it heavier and more unstable.

“It's obvious why it can't swim,” he said.

The giant sail on its back would have made it difficult for a swimming Spinosaurus to stay upright, Dr Myhrvold said. “If it helps even a little bit, it keeps tipping over.”

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In other words, Spinosaurus would flip upside down and struggle to pull its oar out of the water.

In this controversy, there are agreements. Spinosaurus was probably longer and heavier than Tyrannosaurus rex. It lived about 95 million years ago in what is now the Western Sahara, but it was a lush environment with deep rivers. It was also an odd-looking dinosaur, with long spines forming a large sail on its back.

Interest in Spinosaurus exploded in the past decade after Nisar Ibrahim, author of the previous bone density study and now a senior lecturer at the University of Portsmouth in England, discovered a new fossil in Morocco. It was discovered in 1915 by Ernst Stromer, a German paleontologist, and destroyed in an aerial bombardment in Munich in 1944.

In a recent study, Dr. Myhrvold and colleagues argue that paleontologists who make bone density claims use a sophisticated statistical technique without understanding its limitations.

“It's completely misused here,” Dr. Myhrvold said. “Unfortunately, if you have a lot of dense figures, most paleontologists' eyes glaze over.”

Dr. Myhrvold is not a traditional academic. Since leaving Microsoft in 1999, he is best known for leading the development of the encyclopedic Modernist Cookbook. But he has previously fueled esoteric statistical conundrums, criticizing findings about the growth rate of dinosaurs and saying the NASA trove of asteroid data is flawed and unreliable.

A previous study by other researchers found that diving mammals have denser bones than land-dwelling mammals. But other mammals also have dense bones for other reasons. Elephants need strong bones to support their weight.

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In 2022, researchers led by Matteo Fabbri, now a postdoctoral researcher at the University of Chicago, argued in their paper that bone density is a reliable predictor of whether an animal lives in water or on land for a much wider range of species. Extinct species.

“Oh, is it just mammals or is it reptiles?” We thought so. Dr Fabri said in an interview. “If this is true, can we infer ecology in extinct animals, including such odd-looking dinosaurs as Spinosaurus?”

Dr. The analysis showed that “higher bone density was associated with a higher probability of going under water,” says Fabri.

The team of scientists concluded that Spinosaurus and Spinosaurus' relative Baronyx dived, while another related dinosaur, Sucomimus, did not go underwater.

However, Dr. Myhrvold argues that bone density does not divide neatly into two groups. There are many aquatic animals that have less bone density than many land animals. “If the two distributions are close, you can't get a valid result, or at least not have any statistical power,” he said.

He gives an example: In humans, men are generally heavier than women, but not every man is heavier than every woman. So, if someone tells you that someone weighs 135 pounds, you cannot reliably determine whether that person is male or female.

Dr. Myhrvold and Dr. Sereno is now Dr. Fabbri and Dr. Although at odds with Ibrahim, they were all on the same page as co-authors at one time A 2014 article describing a Spinosaurus discovered in Morocco.

“We part ways intellectually,” Dr. Sereno said.

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Dr. Fabri is currently Dr. is in the same department as Sereno, although he will be a professor at Johns Hopkins University this summer.

“We say hello on this sidewalk,” Dr. Fabri said. “That's okay. We're not killing each other, obviously.

Dr. is doing additional research in Morocco. Ibrahim said the further findings would make it even more certain that Spinosaurus was an aquatic creature.

He also dismissed Dr Myhrvold's biomechanical arguments as to why Spinosaurus could not swim, saying much was still unknown. He is Dr. He compared Myhrvold's findings to paleontologists who argued that tyrannosaurs must have been scavengers because they couldn't run fast enough to catch small, fleeting prey. But tyrannosaurs didn't have to be fast to take down a large, slow-moving triceratops.

Similarly, prehistoric African rivers were filled with giant, slow-moving fish, Dr. Ibrahim said. Spinosaurus didn't have to be a skilled swimmer to catch them.

“I can't reveal too much,” he said. “But we have new material. We have a lot of exciting projects.

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