2023-11-25 05:30:25
Japanese researchers have discovered a new species of 70 million-year-old dinosaur in Mongolia that may shed light on the relationship between these animals and birds. The striking thing about this meter-long and possibly feathered specimen is the posture in which it was found: curled up on itself, with its legs bent on both sides of the body, its tail wrapped around them and its head curved backwards, It slept in a similar way to modern birds. The discovery, recently reported in the magazine PLOS ONEsuggests that dinosaurs not only looked like birds but may also have behaved like them.
Paleontologists excavated the dinosaur skull and nearly complete skeleton in the Gobi Desert, in the Barun Goyot Formation in Mongolia, in 2016. Named Jaculinykus yaruui, something like ‘fast clawed dragon’, the small, possibly feathered dinosaur was well adapted to running around what is now Mongolia. With hands dominated by a large thumb, he could have dug into insect colonies in search of food.
But what caught the researchers’ attention is the animal’s posture. Most of the bones were still arranged in the original death pose of the dinosaur, which must have lost its life in its sleep. It was quickly buried under sand, which preserved it for millions of years until it was discovered by paleontologists.
The dinosaur’s head was stuck to its side, resting on its right knee. The hind limbs were bent underneath and most of the tail curved around the left side of the body.
Buried in a sand storm
“Like most of the skeleton of Jaculinykus has remained in its original position, it could have been quickly buried during a sandstorm or catastrophic event,” explains Kohta Kubo, lead author of the study and paleontologist at Hokkaido University in Japan.
“Alternatively, it is possible that it was buried while in a burrow. The alvarezsaurids (a type of theropod – small, carnivorous bipedal dinosaur) such as Jaculinykus “They had tiny but powerful forelimbs that possibly would have allowed them to dig underground tunnels, and if these had collapsed, they would have retained their living position,” says Kubo.
«However, it became buried, and being underground protected it from scavengers. “This ensured that it is one of the best preserved alvarezsaurids from this period, which greatly improved our understanding of its anatomy and ecology,” he adds.
The bird-like sleeping posture may help keep you warm by reducing heat loss during sleep. “Until now, this posture has only been observed in a couple of dinosaurs, including a troodontid known as Mei,” explains Paul Barrett, a dinosaur expert at the Natural History Museum in London. “As occurs later in dinosaur lineages with other bird-like postures, it is reasonable to assume that birds and their close relatives inherited their resting position from a common ancestor,” he says.
However, figuring out what this common ancestor might be is difficult, as fossils of small dinosaurs like alvarezsaurids are often poorly preserved.
The new fossil suggests that this sleeping behavior may have been more common than expected among non-avian relatives of early birds.
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