Himeoolithus

Say it: hee-MAY-oh-LITH-us

Name means: “small egg stone, from Japanese 'hime' meaning small or pretty, and Greek 'oo' and 'lithos' meaning egg stone”1

Ate: MeatMeat-eating dinosEarly Cretaceous

Himeoolithus was a tiny meat-eating dinosaur that lived in what is now Japan about 110 million years ago. It is known from its eggs, which are some of the smallest theropod eggs ever found, about the size of a quail egg. These eggs show that small dinosaurs lived alongside the giants!2

Lived

113 to 110 million years ago3

Early Cretaceous

Fossils found in

Kamitaki Egg Quarry, Hyogo Prefecture, Japan3 2

Food

Meat3

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

cool stuff

Fun facts

Himeoolithus eggs are the smallest non-avian theropod eggs known, with an estimated mass of only 9.9 grams, about the size of a modern quail egg.1

The eggs are unusually elongated for their size, with a length-to-width ratio of 2.25, which is more typical of larger theropod eggs.1

The nest was found in place, not moved by water or wind, because most eggshell fragments were positioned concave-up, which happens when they break in place.2

Over 1,300 eggshell fragments from Himeoolithus were found at the Kamitaki Egg Quarry, along with other small theropod eggs.2

The high diversity of small theropod eggs at this site makes it one of the most diverse Early Cretaceous egg localities known.2

AI-made picture of Himeoolithus — An AI-made picture of how Himeoolithus 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.

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Myth buster

Myth: Some people think all dinosaurs were huge, but Himeoolithus shows that many were small.

Truth: Himeoolithus eggs are tiny, and the dinosaur that laid them was likely small, showing that dinosaurs came in many sizes.2

For dino experts

Scientific name: Himeoolithus
Named by: Tanaka et al. 20203
Group: Meat-eating dinos
Family / clade: Theropoda3
Classification: Theropoda3
Age of the rocks: 113 to 110 million years (Albian)3
Rock formations: Ohyamashimo3
Countries: Japan3
Fossil records: 1 in the Paleobiology Database3
Discovery: The eggs were first discovered in 2015 at the Kamitaki Egg Quarry in Japan, and the species was named by Tanaka and colleagues in 2020.2 3
Still debated: Scientists are not sure exactly which theropod dinosaur laid the eggs, since no bones of the adult have been found yet.2

Where the facts come from

Exceptionally small theropod eggs from the Lower Cretaceous Ohyamashimo Formation of Tamba, Hyogo Prefecture, Japan (sciencedirect.com)
Tiny Japanese Dinosaur Eggs Help Unscramble Cretaceous Ecosystem | Research News - University of Tsukuba (tsukuba.ac.jp)
Himeoolithus in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

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