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Jaculinykus

Name means: “speedy dragon”1

Ate: MeatOdd feathered dinosLate Cretaceous

Jaculinykus was a tiny, bird-like dinosaur that lived in the Gobi Desert. It had a big claw on its thumb and could probably run very fast. One fossil was found curled up like a sleeping bird!1 2

Lived

84 to 72 million years ago5

Late Cretaceous

Fossils found in

Nemegt locality, Ömnögovi Province, Mongolia1 5

Food

Meat1 5

Length

0.5 to 1 m1

estimated from related alvarezsaurids

Weight

2 kg to 5 kg1

Height

0.3 to 0.5 m1

at the hips

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

How tall was it?

at the hips

How heavy was it?

as heavy as 1 house cats

as long as 2 house cats nose to tailas long as 6 bananas end to endabout as heavy as a house catas heavy as 42 bananas

How big was Jaculinykus compared to YOU?

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cool stuff

Fun facts

Jaculinykus had only two fingers on each hand. Its first finger was huge with a big claw, and its second finger was tiny.1 2

The fossil of Jaculinykus was found in a sleeping position. Its neck was curled back and its legs were tucked under its body, just like modern birds.1 2

Jaculinykus is the ninth alvarezsaurid dinosaur discovered in the Nemegt Basin of Mongolia.1 2

Its name means 'speedy dragon' in a mix of Greek and Mongolian. 'Yaruui' means 'speedy' in Mongolian.1

Jaculinykus lived about 83 to 72 million years ago during the Late Cretaceous period.5

This dinosaur was a maniraptoran theropod, meaning it was more closely related to birds than to other dinosaurs like T. rex.1 2

AI-made picture of Jaculinykus — An AI-made picture of how Jaculinykus might have looked, made by a computer from what scientists know. It is a guess: the real animal may have looked different, and nobody knows its true colours.

you asked

Most asked questions about Jaculinykus

?How big was Jaculinykus?

Jaculinykus was a tiny dinosaur, about the size of a modern turkey or a large chicken. Its nearly complete skeleton is small and delicate.1 3

?What did Jaculinykus eat?

Jaculinykus probably ate insects. It had a big thumb claw that it used to dig into insect nests, and its flexible skull may have helped it eat larger, struggling bugs.4

?Did Jaculinykus have feathers?

Yes, Jaculinykus was a feathered dinosaur. It was a maniraptoran theropod, a group that includes birds, and scientists think it was covered in feathers.4

?Why did Jaculinykus have a big thumb?

Jaculinykus had a big thumb with a large claw to help it dig for food, probably insects. The thumb was huge while the other fingers were tiny or missing.4 1

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Myth buster

Myth: Some people think all dinosaurs slept standing up.

Truth: Jaculinykus shows that some dinosaurs slept curled up like birds, with their heads tucked under their arms.1 2

For dino experts

Scientific name: Jaculinykus
Named by: Kubo et al. 20235
Group: Odd feathered dinos
Family / clade: Alvarezsauridae5
Classification: Theropoda > Alvarezsauridae5
Age of the rocks: 84 to 72 million years (Campanian)5
Rock formations: Baruungoyot5
Countries: Mongolia5
Fossil records: 1 in the Paleobiology Database5
Discovery: Jaculinykus was named in 2023 by a team of scientists including K. Kubo, Y. Kobayashi, T. Chinzorig, and K. Tsogtbaatar. The nearly complete skeleton was found in the Baruungoyot Formation of Mongolia.1 5
Still debated: Scientists are still debating exactly how Jaculinykus used its big thumb claw. It might have been for digging for insects or for tearing open logs.1 2

Where the facts come from

A new alvarezsaurid dinosaur (Theropoda, Alvarezsauria) from the Upper Cretaceous Baruungoyot Formation of Mongolia provides insights for bird-like sleeping behavior in non-avian dinosaurs | PLOS One (journals.plos.org)
A new alvarezsaurid dinosaur (Theropoda, Alvarezsauria) from the Upper Cretaceous Baruungoyot Formation of Mongolia provides insights for bird-like sleeping behavior in non-avian dinosaurs (pmc.ncbi.nlm.nih.gov)
Jaculinykus (en.wikipedia.org)
New species of big-thumbed dinosaur discovered in Mongolia | Natural History Museum (nhm.ac.uk)
Jaculinykus in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

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