250 Million Year Old Fossil Embryo Reveals How a Precursor to Mammals Survived the Great Dying

The egg to be scanned or scanned. Sophie Vrard. (The Independent)

JAKARTA - Fossils of embryos that are around 250 million years old help scientists answer a long-standing puzzle about the origins of mammals. They lay eggs or give birth. The latest findings show that the answer is now clearer. It turns out they lay eggs.

Launching a report by The Independent, Tuesday, April 14, the evidence came from an embryo of Lystrosaurus found near Oviston, Eastern Cape Province, South Africa, in 2008 and then stored at the Bloemfontein National Museum. Lystrosaurus is a plant-eating animal from the therapsid group, a group of ancient animals that are the ancestors of mammals, including humans.

So far, many therapsid fossils have been found. What has not been found is the egg. Therefore, it was suspected that some of these animals may have given birth like most modern mammals. This new fossil changes that suspicion.

The problem is, the embryo found did not leave a shell. All that is visible is a small body in a curled position. That's why it took a long time to confirm that this embryo was indeed dead before hatching.

Still according to The Independent report, researchers used high-powered X-rays at the European Synchrotron Radiation Facility in Grenoble, France, to see the inside of the embryonic bone. This research facility allows scientists to read very detailed structures inside the fossil.

From the examination, the researchers found that the lower jaw of the embryonic beak had not yet fully fused. In modern birds and turtles, this condition appears before hatching. The findings strengthen the conclusion that the Lystrosaurus embryo died while still in an egg with a soft shell like a skin.

The value of this finding does not stop at the question of reproduction. The fossil also provides clues about how Lystrosaurus survived the "Great Dying", a mass extinction about 252 million years ago that wiped out about 90 percent of life on Earth.

The report said the Lystrosaurus eggs were allegedly relatively large compared to the size of their mother's body. Large eggs provide two advantages. First, less water is lost, so it is more resistant in dry environments. Second, Lystrosaurus offspring likely hatch in a more mature, or precocial, state, so they eat themselves sooner, avoid predators, grow, and breed.

With such a pattern, Lystrosaurus is suspected to have a greater chance of recovering faster after a major disaster. This finding also adds to scientists' understanding of the origin of mammalian reproduction, including how survival strategies were formed long before modern mammals emerged.