How small is the smallest dinosaur egg?

The smallest dinosaur egg, featured inside the yellow circle.

A group of scientists had discovered the world's smallest dinosaur egg fossil, measuring approximately 4.5 cm by 2 cm, in western Japan.

This fossilized egg, which is believed to have weighed just over 10 grams over 100 million years ago, was recovered from sediment layers dating back to the early Cretaceous Period in Tamba, Hyogo Prefecture, as reported by the research team.

The team, consisting of researchers from the University of Tsukuba and the Museum of Nature and Human Activities, Hyogo, and others, conducted a thorough analysis of the fossil and concluded that it most likely belonged to a small non-avian theropod dinosaur.

The team's extensive research spanned the years from 2015 to 2019. During this period, they surveyed sediment layers dating back 110 million years and uncovered four fossilized eggs, alongside an astonishing 1,300 scattered fragments of eggshells. The newly discovered egg, named Himeoolithus murakamii, has been identified as one of four distinct types found in the region.

This groundbreaking discovery suggests that diverse species of small dinosaurs were once nesting together in this region, which is renowned as one of the world's most abundant sites for Lower Cretaceous fossilized eggs.

What is the largest dinosaur egg?

The largest dinosaur eggs.

The title of the largest known dinosaur eggs is held by a group known as the egg genus Macroelongatoolithus, which encompasses fossilized theropod eggs discovered both in North America and Asia. These eggs display a distinctive elongated shape, akin to a French bread loaf, typically measuring approximately three times their width and have been documented to reach astonishing lengths of up to 61 cm (2 feet).

One of the most notable finds among these colossal dinosaur eggs was made in China's Henan province back in 1992. This particular discovery constitutes a partial clutch consisting of five discernible eggs. The longest of these eggs measures 45 cm (18 inches) in length and approximately 15 cm (6 inches) in width. Remarkably, resting atop this clutch was the preserved body of a juvenile theropod dinosaur.

The remarkable size of these eggs initially raised speculations regarding their origin, with some pondering whether they might be linked to the formidable theropod, Tyrannosaurus rex. The baby dinosaur found in association with these eggs, seemingly expelled from its egg forcibly, retains its embryonic posture, featuring its chin tucked down towards its chest and its hips positioned forward and upwards. Measuring 23 cm (9 inches) in length, extending from the top of the skull to the base of the tail, this diminutive dinosaur would have occupied just a fraction of the largest egg beneath it. This further corroborates the notion that it was indeed in an embryonic state.