Updated

Updated · Yahoo! Voices · Aug 24

Antarcticoolithus bradyi Sets 29-cm Record as Antarctica’s Largest Soft-Shelled Egg

Updated

Updated · Yahoo! Voices · Aug 24

Antarcticoolithus bradyi Sets 29-cm Record as Antarctica’s Largest Soft-Shelled Egg

Q: What massive, unidentified sea monster left behind a giant soft-shelled egg in ancient Antarctica?

The giant soft-shelled egg was most likely laid by a mosasaur, a huge marine reptile, but scientists cannot identify the exact species. Researchers say the 68-million-year-old fossil from Seymour Island, Antarctica, has a thin, leathery shell structure more like the eggs of snakes and lizards than the hard shells typical of dinosaur eggs. That points away from dinosaurs and toward a large marine lepidosaur, with a mosasaur considered the strongest match. The egg, formally named *Antarcticoolithus bradyi*, is about 29 by 20 centimeters and is the largest soft-shelled egg ever found. No bones were attached to it, so the parent remains officially unknown. Still, the morphology fits mosasaurs found in the same region far better than any known dinosaur egg of comparable size. One leading candidate is *Kaikaifilu hervei*, a large Antarctic mosasaur known from nearby fossils, but researchers have not proved that link. The discovery is important because it suggests some mosasaurs may have reproduced by laying soft, thin-shelled eggs—or eggs that hatched almost immediately—rather than only giving birth to live young. So the “massive, unidentified sea monster” was most plausibly a mosasaur, possibly a species such as *Kaikaifilu hervei*, though the exact animal is still unknown.

1 articles · Updated · Yahoo! Voices · Aug 24

A 29-by-20 cm fossil egg from Antarctica has been identified as the largest soft-shelled egg ever found and the second-largest egg known overall, dating to about 68 million years ago.
Its leathery structure matches snake and lizard-like eggs more than dinosaur eggs, leading researchers to propose a mosasaur—large marine lepidosaurs found nearby—as the likely layer, though no embryo or bones were preserved.
The find, published in Nature, was distinct enough that scientists created a separate eggshell taxon, Antarcticoolithus bradyi, and said it strengthens the idea that mosasaurs reproduced with thin-shelled or near-viviparous eggs.
Minerals in the fossil site—apatite and pyrite—suggest the shell was buried under the seafloor in oxygen-poor conditions, helping explain how such a fragile soft shell survived to fossilize.