
The anatomy of Jaculinykus yaruui. The black line indicates 10-centimeter-width.
16:43 JST, November 23, 2023
SAPPORO (Jiji Press) — A research team including Hokkaido University has discovered in Mongolia the skeleton of a new dinosaur, curled up in a position like that of a sleeping modern-day bird.
In August 2016, the team, including Hokkaido University Prof. Yoshitsugu Kobayashi, unearthed the nearly complete fossil skeleton of the dinosaur, named Jaculinykus yaruui, which means “speedy dragon claw.”
Believed to be from around 70 million years ago during the Late Cretaceous period, the new alvarezsaurid dinosaur specimen was discovered in the Nemegt area in the southwestern part of the Gobi Desert in a joint excavation project with a Mongolian institute.
While alvarezsaurid dinosaurs had birdlike features, the team found that the Jaculinykus yaruui is a new species because of its unique features, such as a large protrusion near its tibia.
According to the team, the specimen was found with its head tucked into its body and its legs folded, much like when modern birds sleep. The team believes that the posture was associated with heat conservation.
The team said that, through the discovery of the fossil remains, it has been able to trace the history of avian sleeping behavior further.
The focal point of the discovery is that a dinosaur behavior was preserved, something rarely seen in fossils, Kobayashi said, noting the importance of the finding for research into how dinosaurs evolved into birds.

An image of a Jaculinykus yaruui.
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