Seiji Yamamoto
An illustration of a newly discovered dinosaur species, Jacrynyx yarui, shows it sleeping in a position similar to that of modern birds.
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Death in the wild is often brutal and violent. But for one small, bird-like dinosaur from the Late Cretaceous period, the end of its life was relatively uneventful. He curled up and took a nap, never waking up.
That’s what scientists have interpreted from the poses of dinosaur fossil skeletons. Its cozy posture is with its head resting on its limbs and its tail wrapped tightly around its body. modern birds This suggests that these dinosaurs not only looked like birds, but may have acted like birds.
Paleontologists unearthed a dinosaur skull and nearly complete skeleton in Mongolia’s Barun Goyot Formation in the Gobi Desert, with most of the bones still arranged in the animal’s natural death pose, researchers said in an academic report on Wednesday. It was reported in a magazine. Pro Swan.
The animal’s long neck was wrapped around the right side of its torso, and its head rested on its right knee, snug against its side. The hind legs were folded underneath, and most of the tail was curved along the left side of the body.
The study authors identified it as a small alvaresaurid. theropod It had a long tail, legs, and short forelimbs (a bipedal carnivorous dinosaur). Alvarezsaurids are part of a larger group of dinosaurs called maniraptorans, which includes birds and their related bird-like dinosaurs.
The posture of the tiny Alvarezsaurus mimicked that of two other dinosaur fossils found in Mongolia, Sinornithoides yongi and Mei Long, who also curled up in a bird-like sleeping position. Both dinosaurs are members of the Troodontidae family, another member of the maniraptoran family, and are more closely related to birds than Alvarezsaurus.
Kota Kubo
Jaculinykus yaruui lived about 70 million years ago. (A) Photo of a fossil skeleton discovered in the Gobi Desert of Mongolia. (B) Illustration shows the skeletal elements with the skull in green and the pectoral girdle and forelimbs in red. (C) Reconstruction of the dinosaur. Gray areas indicate missing areas.
This new fossil suggests that this sleeping behavior may have been more common than expected among non-avian relatives of early birds, the researchers reported.
“You’ve probably seen ducks sleeping with their heads tucked under their wings. And then you see this little dinosaur in the exact same sleeping position,” says Chicago Field Nature. said paleontologist Dr. Jingmai O’Connor, associate curator of fossil reptiles at the Museum of History.
“This is concrete evidence of a behavior that is unique among birds today. Now, we can actually say that this is not a characteristic unique to birds,” O’Connor, who was not involved in the study, told CNN. told.
Scientists who examined this fossil determined that it was a new species to science and gave it the terrifying name Jaclinycus yaloui. The genus name is derived from the mythical dragon He Jaculus and the ancient Greek word onykus, meaning claw, and the species name is derived from the Mongolian word yaruu, meaning hasty or swift.
Jaculinykus yaruui lived about 70 million years ago, BC. Cretaceous period (about 145 million to 66 million years ago), it would have been just over 3 feet (1 meter) long from nose to tip of the tail, says the study’s lead author, a paleontologist and Hokkaido University paleontologist. said Kota Kubo, a doctoral candidate in the group. Japan.
“When discovered, this specimen was thought to be a partial skeleton, but after preparation, it is a nearly complete, articulated skeleton in a life-like posture,” Kubo said in an email. told CNN. “This is the first definitive record of this posture in alvaresaurid and early branching maniraptorian dinosaurs.”
Kubo said Jaclinycus yaloui’s closest relative is a small alvaresaurid named Shubuia deserti. Some of the features that distinguish this animal include the shape of its nostrils, the attachment of its jaw muscles within its skull, and the shape of its limb bones.
“This is an amazing specimen, and it’s always exciting to learn about new diversity in dinosaurs, especially the alvarezaurid family,” O’Connor said.
Alvarezsaurids are not the best-known group of dinosaurs, but they have long fascinated scientists with their significantly shortened forearms and hands. In some species, he has one huge finger with a spike-like claw at the tip.
“Fossils of this kind that are well-preserved enough to record behavior are incredibly rare,” O’Connor said. “It’s great to have additional evidence that clearly shows this sleeping position was more widespread.”
In modern birds, such behavior helps maintain body temperature. The study suggests that maniraptoran dinosaurs, which also curled up while sleeping, likely had a similar purpose. Alvarezsaurus decreased in size during evolution. This “significant downsizing” may have led non-avian dinosaurs to adopt the same thermoregulatory strategies as their avian relatives, Cobb said.
Moreover, the sleepy little Jaclinycus yalui “highlights that this bird-like thermoregulatory behavior evolved before the origins of powered flight,” he added. “Jaclinycus is an important example of how alvaresaurids have more similarities with living birds, not only in osteological features but also in behavioral traits.”
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works magazines.
