A team of researchers have discovered a new type of egg fossil that is smaller than a golf ball. With a size of approximately 45 x 20 millimetres, it has earned the Guinness World Records title for the smallest fossilized non-avian dinosaur egg.

The egg fossil was found in Tamba City, Hyogo, Japan, which is known to be one of the most significant sites for discovering dinosaur fossils, as soils from the Lower Cretaceous period – which was approximately 110 million years ago – are exposed.

Actual fossil with the egg marked with white arrows (Credit: University of Tsukuba/Museum of Nature and Human Activities, Hyogo)

In a recent discovery, they have found a new type of theropod egg fossil that is around 45 mm tall and 20 mm wide, and weighs only around 10 grams – close to the weight of a quail egg. 

The dinosaur has subsequently been named Himeoolithus murakamii, with “hime” meaning small and cute in Japanese, and “murakamii” being derived from Shigeru Murakami, who first discovered Tambatitanis (a genus of titanosauriform dinosaur) in 2006.

The team of researchers who discovered this fossil includes Kohei Tanaka, assistant professor of the University of Tsukuba, as well as researchers from University of Calgary, The Royal Tyrrell Museum of Palaeontology, and the Museum of Nature and Human Activities, Hyogo.

Members of the research team who discovered the smallest dinosaur egg fossil (Credit: University of Tsukuba/Museum of Nature and Human Activities, Hyogo)

“I would be ecstatic if the new record becomes an opportunity for people to realize that record-breaking dinosaur fossils can be discovered in Japan. I hope it will also bring people to think about the wide variety of dinosaurs that lived in the ancient times. I will continue to uncover the mysteries surrounding the dinosaurs’ habitat and their evolution.” – Kohei Tanaka, assistant professor at the University of Tsukuba