Massive Reptile Discovered in the Belly of a Triassic Megapredator

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Ichthyosaur Specimen on Display

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This image reveals the ichthyosaur specimen with its stomach contents noticeable as a block that extrudes from its body. Credit: Ryosuke Motani

When paleontologists digging in a quarry in southwestern China discovered the almost total skeleton of a giant, dolphin-like marine reptile called an ichthyosaur, they didn’t anticipate to discover another fossil in its stomach. This 2nd skeleton came from a four-meter-long, lizard-like marine reptile called a thalattosaur and is among the longest fossils ever discovered in the stomach of an ancient marine reptile. While the scientists can’t state for sure whether the thalattosaur was scavenged or preyed upon, their work might be the earliest direct proof that Triassic marine reptiles like ichthyosaurs — formerly believed to be cephalopod feeders — were peak megapredators. The findings appear today (August 20, 2020) in the journal iScience.

“If you look across all the similar marine reptiles that lived in the age of dinosaurs, we’ve actually never found something articulated like this in the stomach,” states co-author Ryosuke Motani, a teacher of paleobiology at the University of California, Davis. “Our ichthyosaur’s stomach contents weren’t engraved by stomach acid, so it should have passed away rather not long after consuming this food product. At initially, we simply didn’t think it, however after investing numerous years checking out the dig website and taking a look at the very same specimens, we lastly had the ability to swallow what we were seeing.”

Ichthyosaur and Thalattosaur Dig Site

This image reveals the quarry dig website where ichthyosaur and thalattosaur were discovered, now part of the Xingyi Geopark Museum in China. Credit: Ryosuke Motani

Because stomach contents are hardly ever discovered in marine fossils, scientists count on tooth and jaw shapes to discover what ancient types might have consumed. While ancient peak predators are usually believed to have big teeth with sharp cutting edges, some contemporary predatory types like crocodiles utilize blunt teeth to take in big victim products with comprehending force rather of cutting. Ichthyosaurs share these blunter teeth, however without any direct proof of big victim intake in these ancient marine reptiles, researchers thought that they fed upon little victim like cephalopods.

However, the discovery of the huge thalattosaur in the stomach of the ichthyosaur discovered by Motani, Da-Yong Jiang, a paleontologist at Peking University in China, and their group recommends that this was not the case. “Now, we can seriously consider that they were eating big animals, even when they had grasping teeth,” states Motani. “It’s been suggested before that maybe a cutting edge was not crucial, and our discovery really supports that. It’s pretty clear that this animal could process this large food item using blunt teeth.”

Ichthyosaur's Teeth

This image reveals the ichthyosaur’s teeth, with the damaged white line showing the approximate gum line of the upper jaw. Credit: Jiang et al./iScience

While the scientists now understand that the ichthyosaur might consume animals as big as the thalattosaur, they don’t understand if it eliminated this specific, or just scavenged it. “Nobody was there filming it,” states Motani. However, there is factor to think this was not a case of scavenging: contemporary marine decay research studies recommend that if delegated decay, the thalattosaur’s limbs would break down and separate prior to the tail. Instead, the scientists discovered the opposite in these fossils. The thalattosaur’s limbs were at least partly connected to its body in the stomach, while a detached tail was discovered numerous lawns away, leading the scientists to think it was swindled and left by a predator like the ichthyosaur.

Whether or not the ichthyosaur eliminated its last meal, the fossil offers the earliest direct proof that these huge marine reptiles taken in animals bigger than people. “We now have a really solid articulated fossil in the stomach of a marine reptile for the first time,” Motani states. “Before, we guessed that they must have eaten these big things, but now, we can say for sure that they did eat large animals. This also suggests that megapredation was probably more common than we previously thought.”

The group is still excavating the website where the set of fossils were discovered, which has actually now been become a museum. “We’ve been digging in that particular quarry for more than ten years now, and still, new things are coming out,” states Motani. “At this point, it’s beyond our initial expectations, and we’ll just have to see what we’ll discover next.”

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Reference: “Evidence Supporting Predation of 4-m Marine Reptile by Triassic Megapredator” by Da-Yong Jiang, Ryosuke Motani, Andrea Tintori, Olivier Rieppel, Cheng Ji, Min Zhou, Xue Wang, Hao Lu and Zhi-Guang Li, 20 August 2020, iScience.
DOI: 10.1016/j.isci.2020.101347

This work was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, and the National Geographic Society Committee for Research and Exploration.



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