Not a dinosaur, an ostrich, this is the species that lays the biggest eggs on the planet.

(Dan Tri) - In the vast world of extinct animals, there were eggs so huge that today's ostrich eggs are surprisingly small.

Nowadays, when talking about giant eggs, the first image that comes to many people's minds is probably ostrich eggs.

Weighing in at a record 2,589kg, equivalent to that of a small house cat, the ostrich egg deserves the title of the largest egg laid by a living bird.

From left to right are eggs from elephant bird, moa, ostrich, mute swan, murre, chicken, little owl and oriole (Photo: Denis Bourez).

However, if we look back at the evolutionary history of the Earth, ostrich eggs have become surprisingly small.

About 1,000 years ago, giant birds measuring 3m tall lived and laid eggs all over Madagascar. They were called elephant birds, with two large genera, Aepyornis and Mullerornis.

The elephant bird Aepyornis maximus is believed to be the largest bird that ever lived, weighing up to 1,000kg. It also holds the impressive record for laying the largest eggs of any known animal.

Elephant bird eggs are about 150 times larger than a typical chicken egg. They are so large that the Buffalo Museum of Science once mislabeled one because it was so large it was hard to believe it was a real egg.

Second on the list is a creature that lived during the time of the dinosaurs but was not a dinosaur. Scientists working in Antarctica reported a strange discovery: a giant egg nearly the size of an elephant bird egg.

The size of “The Thing” compared to a human (Photo: Legendre).

Estimated to date back around 66 million years, the rugby ball-sized egg is the first soft-shelled egg fossil ever found on the Antarctic continent. Scientists believe it was laid by a mosasaur, a giant marine reptile.

“It came from an animal the size of a large dinosaur, but it was completely different from a dinosaur egg,” said lead author Lucas Legendre, a researcher at the University of Texas at Austin. The egg was very similar to that of lizards and snakes, but came from a giant relative of theirs.

It was previously believed that giant marine reptiles from the Cretaceous period did not lay eggs, but this mysterious fossil has challenged that view. Scientists have dubbed the 11-by-7-inch rock-like fossil simply “The Thing.”

The next name we can mention is the dinosaur named Beibeilong sinensis. This dinosaur lived 90 million years ago and laid eggs four times larger than today's ostrich eggs, with a diameter of about 45cm and a weight of 5kg.

However, there is another record that has nothing to do with absolute size but with relative proportion: the kiwi, a tiny bird, but one that faces a huge “task” when it comes to pregnancy: their eggs can account for up to 20% of the mother's body weight.

Interestingly, the kiwi is also the closest living relative of the elephant bird, creating a strange connection between two birds with completely different records.

Source: https://dantri.com.vn/khoa-hoc/khong-phai-khung-longda-dieu-day-la-loai-de-ra-trung-to-nhat-hanh-tinh-20250908000203746.htm