An enormous fossilized egg of an extinct marine reptile has been discovered within the 68-million-year-old nearshore marine deposits in Antarctica.
An artist’s rendering of a pair of mosasaurs and their egg. Picture credit score: Francisco Hueichaleo.
Named Antarcticoolithus bradyi, the brand new fossil is the primary fossilized egg present in Antarctica.
The specimen exceeds eggs of all recognized non-avian dinosaurs in quantity and differs from them in construction.
Measuring 29 by 20 cm (11.four by 7.9 inches) and weighing 6.5 kg, it’s the largest soft-shell egg ever found and the second-largest egg of any recognized animal. Though the elephant hen egg is barely bigger, its eggshell is roughly 5 occasions thicker.
College of Texas at Austin paleontologist Lucas Legendre and his colleagues from the USA and Chile suppose that Antarcticoolithus bradyi was laid by an enormous marine reptile, corresponding to a mosasaur — a discovery that challenges the prevailing thought that such creatures didn’t lay eggs.
“The fossil egg is from an animal the dimensions of a giant dinosaur, however it’s fully in contrast to a dinosaur egg. It’s most just like the eggs of lizards and snakes, however it’s from a really large relative of those animals,” Dr. Legendre mentioned.
A diagram exhibiting the Antarcticoolithus bradyi egg, its components and dimension relative to an grownup human. Picture credit score: Legendre et al, doi: 10.1038/s41586-020-2377-7.
The researchers discovered a number of layers of membrane that confirmed that Antarcticoolithus bradyi was certainly an egg.
“The construction is similar to clear, quick-hatching, eggs laid by some snakes and lizards in the present day,” Dr. Legendre mentioned.
Nevertheless, as a result of the fossil egg is hatched and accommodates no skeletal materials, the scientists had to make use of different means to zero in on the kind of reptile that laid it.
An artist’s interpretation of a child mosasaur rising from an egg. Picture credit score: Francisco Hueichaleo.
They compiled an information set to match the physique dimension of 259 residing reptiles to the dimensions of their eggs.
They discovered that the reptile that laid the egg would have been 7 m (23 toes) lengthy from the tip of its snout to the top of its physique, not counting a tail.
Including to that proof, the rock formation the place the Antarcticoolithus bradyi egg was found additionally hosts skeletons from child mosasaurs and plesiosaurs, together with grownup specimens.
“Many authors have hypothesized that this was form of a nursery web site with shallow protected water, a cove setting the place the younger ones would have had a quiet setting to develop up,” Dr. Legendre mentioned.
The study was printed within the journal Nature.
L.J. Legendre et al. An enormous soft-shelled egg from the Late Cretaceous of Antarctica. Nature, printed on-line June 17, 2020; doi: 10.1038/s41586-020-2377-7