The guts of voracious carnivorous dinosaurs preserved in an exceptionally rare fossil
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More than 100 million years ago, a terrifying bird-like dinosaur was swept into a lake and transformed into an exceptional fossil in what is now China, preserving one of the few intact gut remains known from non-avian dinosaurs, a new study finds.
Paleontologists knew they had unearthed something special when they saw “a large bluish layer in the belly” of the fossilized beast, which belongs to the newly discovered species Daurlong fragrant, as well as a dinosaur lineage called the dromaeosaurids, which included the ancestors of modern birds. This bluish coating had “exceptional preservation” of the dinosaur’s gut, the researchers wrote in the study, published in the journal Scientific Reports (opens in new tab) on Nov. 19.
The finding provides valuable insight into both bird and dinosaur gut evolutiongiving researchers a clearer picture of meal times during the Lower Cretaceous Period (145 million to 100.5 million years ago).
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Dromaeosaurids – also known as “raptors” – like D. fragrant were usually small, feathered and carnivorous. This group roamed the Soil from the middle Jurassic (about 167 million years ago) to the end of the Cretaceous era (66 million years ago). Their ranks include some of pop culture’s most famous dinosaurslike Velociraptor and Deinonychos. But despite their popularity, little is known about their actual guts.
Soft tissue preservation is rare for any fossil, and gut preservation is particularly unusual among dinosaurs. “This is the first case among dromaeosaurids,” study co-author Andrea Cau, an independent paleontologist based in Parma, Italy, told Live Science in an email.
The conditions for the solidification must be just right to prevent spoilage bacteria from eating away at delicate soft tissues, such as cartilage and organs. The newly described D. fragrant specimen was likely buried very quickly under soft, fine sediments at the bottom of a body of water in what is now the Jehol Biota – an area known for well-preserved fossils in modern-day Inner Mongolia, an autonomous region in northern China. There, in the low-oxygen environment where aerobic bacteria couldn’t survive, the dinosaur remains mineralized into fossils.
The researchers named the genus of the dinosaur “Daurlong,” after the Daur people of Inner Mongolia and “long,” the Chinese word for “dragon.”fragrant‘ honors Wang Junyou, the director of the Inner Mongolian Museum of Natural History.
The remarkable preservation provides insight into how D. fragrant lived, and what it could have eaten. As far as the researchers could tell, the gut resembles the few other remains known from carnivorous dinosaurs, suggesting that more omnivorous dromaeosaurid gut plans did not evolve until the dawn of modern birds after the Cretaceous Period. It turns out D. fragrant ate small prey, such as mammals (which were no larger than badgers during the Mesozoic Era), fish, other small dinosaurs, and possibly amphibians. “Given the abundance of frogs and other amphibians in the Daurlong place,” it’s possible that this dromaeosaurid preyed on frogs and salamanders, Cau said.
although D. fragranthis intestines were preserved, his stomach was not. Perhaps the “extremely acidic environment of the stomach immediately after the animal’s death” prevented it from mineralizing and turning into a fossil, the researchers wrote in the study.
Unlike their depiction in the 1993 movie “Jurassic Park,” most dromaeosaurids were relatively small and lightweight. D. fragrant itself was just under five feet tall from tip to tail, about the size of a pony. And, like other members of his family, he wore feathers.
In the future, Cau and his team plan to investigate the specimen more closely to gain more insight into its feathers, life and possibly death. “Our hope is to find some information about plumage color in life and to better reconstruct the peculiar circumstances that led to soft tissue preservation,” he said.
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