You can’t make a mammal-ette without laying some eggs.
Surprisingly, the duck-billed platypus isn’t the only egg-laying mammal. Fossil analysis in South Africa reveals that mammalian ancestors were laying hard-shelled embryos around 250 million years ago. This exciting find was detailed in a study published in Plos One.
According to study author Jennifer Botha from the University of the Witwatersrand, “This discovery breaks entirely new ground.” The fossil belonged to a therapsid, a group that gave rise to modern mammals, including humans, as explained by The Conversation.
Therapsids were first identified over 150 years ago through fossils found in the same region. Researchers knew some prehistoric species laid eggs, but evidence specific to therapsids was missing—until now.
The fossil, discovered in Oviston, South Africa, in 2008 by paleontologist John Nyaphuli, belonged to an animal called Lystrosaurus. This pig-like herbivore had a turtle-like beak and unique features like naked skin and tusks.
At first, scientists didn’t realize the fossil had hatched from an egg. Recent developments allowed them to use X-ray techniques to analyze its state of development. They found that the tiny Lystrosaurus embryo had yet to fuse its beak, suggesting it was preparing to break free from its shell.
The researchers noted, “This developmental trait only appears in modern turtles and birds, where jaw bones fuse before birth.” The Lystrosaurus embryo, however, died in the egg, tightly nestled within its leathery shell.
Botha emphasized that this marks a significant milestone in understanding our mammalian ancestors. Currently, only two types of egg-laying mammals exist: the duck-billed platypus and the echidna.
The reproductive habits of the Lystrosaurus hold more than just historical interest. They likely played a crucial role in the species’ survival during a massive extinction event about 252 million years ago, known as the “Great Dying.” This event wiped out around 90% of life on Earth.
The large size of the Lystrosaurus’ eggs meant that their young were better equipped for survival, weaning on yolk instead of milk, which gave them a better chance in a hostile world. The leathery eggs lost less water, making them less susceptible to drying out—a critical advantage during that arid time.
Additionally, advanced hatching stages meant young Lystrosaurs could fend for themselves more quickly, escaping predators and reproducing faster than other species. Growing up swiftly could have been the key to survival during cataclysmic events.
This discovery not only illuminates the reproductive origins of modern mammals but also provides insights into how certain species endure through environmental catastrophes. Understanding these patterns can potentially inform current discussions on biodiversity and extinction risks today.
Source link
Science,fossils,study says
