A life-size skeleton model of Spinosaurus aegyptiacus, it is the largest carnivorous dinosaur ever found. PHOTOGRAPH BY REBECCA HALE
uux.cn According to National Geographic (author: Michael Greshko, ed.: Yishan Shi): The new study claims that while spinosaurus is closely related to water, it may not be inherently unfit to dive into the water to catch fish.
About 100 million years ago, a dinosaur about 15 meters long roamed the coastline of ancient Morocco and preyed on fish and other animals with its crocodile-like head. But scientists debate exactly how the predator, called Spinosaurus aegyptiacus, hunted in the water.
In 2014, National Geographic Emerging Explorer Nicha. In a sensational paper, Nizar Ibrahim argued that Spinosaurus spent most of his time in the water. Perhaps it was able to hunt aquatic life by swimming —or even diving—and was the first dinosaur known to have done so. However, a new study now claims that although spinosaurs love to eat fish, they may not be able to swim at all.
The analysis, published in the scientific journal PeerJ in mid-August, used computer simulations to infer how the creature floated. The results showed that spinosaurs were too buoyant to easily dive into the water while chasing prey, and their slender, somewhat top-heavy body also made it easy for spinosaurs to fall sideways in the water.
"I've pointed out what I think is a problem with the hypothesis [of the Ibrahim team], and if they can't come up with new evidence to refute it, then their hypothesis – to use my parable – dies in the water," don said. Don Henderson said he was the dinosaur curator at the Royal Tyrrell Museum of Paleontology in Alberta, Canada, and the author of the new study. "If science is self-correcting, this is an example of self-correction in progress."
While it is not yet possible to draw conclusions about the "seaworthiness" of Spinosaurus, these findings are enough to revive the debate about how the largest known carnivorous dinosaur filled its stomach.
"This study looks quite convincing and shows that Spinosaurus did not have a body form that was particularly adapted to diving or swimming underwater," said Tom Thompson, a paleontologist at the University of Maryland. Tom Holtz said he was not involved in the study.
Almost sinking?
Regardless of how this dinosaur moved in the water, Egyptian spinosaurs and their relatives in the family Achiosaurus relied on aquatic ecosystems to survive. Fish scales have been found in the stomachs of many spinosaurs, and the skeletons of these dinosaurs have been unearthed in areas that were once coastal or riverbed.
The jaws of the spinosaurus family are very similar to those of the modern fish-eating grey moray eel; the jaws of both animals are flat and narrow, and the conical sharp teeth are arranged in a petal-like arrangement at the tip of the mouthpart, suitable for catching slippery fish in the obscure water. On top of that, chemical imprints on the remains of the spinosaurus family show that these animals spent a great deal of their lives in the water, like crocodiles today.
"We've seen a number of very exciting papers that add more evidence to the semi-aquatic habits of Spinosaurus," said Ibrahim, a paleontologist at the University of Portsmouth. "As for how these animals move and hunt in the water, that's obviously the more puzzling part of scientific research."
To demonstrate the water power of Spinosaurus, Henderson built a 3D model of Spinosaurus based on the skeleton reconstructed by Ibrahim in 2014. He paid special attention to the sails on the back of spinosaurus, which weighed hundreds of kilograms and extended more than 1 meter high. To test his approach, Henderson modeled both alligators and emperor penguins, both of which exhibited the same buoyancy as the real world in his simulations.
Henderson first wanted to see if spinosaurus could keep its head on the water while floating. His simulations say yes, but only similar to other related dinosaurs, including Tyrannosaurus and Baryonyx. He also found that spinosaurus should "not sink": even considering its high bone density, or the fact that spinosaurus might spit out three-quarters of the air in its lungs, it was still difficult to dive underwater.
Henderson's model also showed that the center of mass of spinosaurus was located between the hind feet and the hind feet, meaning it should be suitable for walking on the hind limbs. This is contrary to Ibrahim's findings, whose research puts the mass center of spinosaurs much further ahead, suggesting that the animal should be more comfortable walking on land on land.
Then again, Spinosaurus's hind limbs were unusually short, and compared to his relatives, it resembled a dachshund among dinosaurs. "No matter how much it is measured, its legs are short and thick," Hodz said. "Spinosaurus is not good at running around."
Henderson then studied whether Spinosaurus could remain stable in water. He built cross-sectional models of spinosaurus and american alligators, and then rammed both animal models until they were tilted to a 20-degree angle. The alligator's profile model resembles a slightly inclined canoe, first rocking back and forth, and finally stabilizing. However, the cross-sectional model of Spinosaurus flipped sideways and could not be corrected.
"All of today's semi-aquatic animals — turtles, marine mammals — don't tip over easily; they don't have to struggle to maintain their posture at all times so that their body parts are perpendicular to the surface of the water," Henderson said. "Keeping your body perpendicular to the surface of the water is not a natural posture."
Waterfront living
In mid-August, Ibrahim embraced Henderson's research in a telephone interview, though he also expressed some doubts.
One of the points he said is that Henderson's model did not use the spinosaurus skeletons that Ibrahim participated in the tissue rehabilitation as a baseline. He adds that building computer models of ancient animals, like all paleontological studies, would be faced with the problem of mispronunciation. Future models will benefit from incremental fossils; Ibrahim said paleontologists have discovered and officially documented more spinosaurus bones.
"It's always good to use modeling techniques, but we need more models, and we need more models that are really fossil-based," he said. "The truth is in the bones, not in the computer."
Hodz added that Spinosaurus is also likely to be in the early evolutionary stages of the semi-aquatic life form. "When an act first starts, you may not be equipped all at once," he said. These evolutionary adaptations take time to develop.
As for Henderson, he imagines spinosaurs like grizzly bears: a fish-eating machine that comes and goes in shallow waters.
Paleontologist David M. Thompson of Queen Mary University of London. David Hone adds that swimming skills are by no means a test strip for aquatic lifestyles.
"Herons don't swim, but they spend most of their time in knee-deep water, wading around the edge of rivers," he said. "It may be a little reluctant to say 'semi-aquatic', but the ecology of this animal is definitely fundamentally related to water."
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