The platypus is in many respects an evolutionary marvel. It has a beak and lays eggs, but it is still a mammal. This is what makes them so special today: they are, along with the echidna, the only mammals that lay eggs, called cloacae. During the Cretaceous period there were many of these amazing features in Australia. This is clear from a study published in 2024 in a specialized journal The sheringa.
Eye-catching appearance
Biologist George Shaw was one of the first scientists to see a platypus. At first he thought they were joking with him. An animal with a toothless beak, a beaver tail, and the feet of an otter? It must have been assembled manually. But no, the animal already existed, he had to deduce.
No one now doubts the existence of platypus, but they remain strange creatures. It has both reptilian (cloacal) and mammalian (warm-blooded and milk-producing) characteristics. How did this animal continue to evolve? More clarity on this matter has come thanks to a discovery made more than twenty years ago.
In the opal mines of Lightning Ridge, Australia, paleontologist Elizabeth Smith and her daughter found fossilized teeth and jawbones. They donated it to the Australian Museum, but there it was put in a drawer and forgotten about. Until two years ago. After extensive analysis, the researchers, including Smith, present their findings.
New species of cloacal animals
It turned out that the fossilized remains belonged to six carnivorous animals, three of which were previously unknown. The most striking species have been named Opalius is great. Its anatomy is very similar to the platypus (“platypus” in English), but its jaw and snout are more similar to the echidna. That's why researchers jokingly called it “Echidnapus.”
The remains are about one hundred million years old. This makes them slightly younger than the oldest known cloacal bird, tinolophus trussleri, That walked on Earth one hundred and thirty million years ago. This species still has five molars, whereas modern cloacal animals are toothless. This shift is reflected in newly discovered fossils. Some had only three molars, while others had as many as five.
The final transition to a toothless existence probably began about two million years ago. Then the Australian water vole appeared on the scene, which had a similar diet to the platypus. They then move on to softer, more slippery food, such as worms, larvae, and small fish. A beak covered with tough leathery skin is more suitable for this purpose.
Continent with platypus
What the study also showed, according to the researchers, is that egg-laying mammals were much less rare during the Cretaceous period than previously thought. The fact that three new species have been found – all possessing a set of previously unknown characteristics – proves that the family of egg-laying mammals is extremely complex. There were probably countless different species of cloacal animals roaming Australia. As research leader Tim Flannery says: “It's like discovering a completely new civilisation.”
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Rolene is a freelance science journalist. She contributes to National Geographic and KIJK magazine, among others. She loves travel, religious history, and brisk walking.
