Didelphodon

Mesozoic mammals reaching for the stars

Little is known about the early history of mammals. All that is known is that the first monotremes, egg-laying representatives of this species, evolved during the Mesozoic around 145 million years ago.

For a long time, it was believed that mammals remained an insignificant group of small, shrew-like, prowling omnivores for millions of years after their appearance. But a few years ago, dog-sized Cretaceous mammals were found in China. And some of these mammals apparently did not disdain smaller dinosaurs as food.

The egg-laying mammals are still represented today by the platypus and the echidna. About 15 million years after the egg-laying mammals, the marsupials appeared on the scene.

Didelphodon was one of these and tiny compared to the dinosaurs that dominated the Cretaceous, but at one metre tall, it was quite large for a mammal of its time. Like many Mesozoic mammals, it was probably nocturnal to avoid the large, carnivorous predators. As a warm-blooded mammal, it was constantly foraging for food, and its dentition, studded with many different teeth, shows that it was a scavenger.

The first placentals, mammals that supply the foetus in the womb with oxygen and nutrients via the placenta, date from around the same time. The majority of mammals living today are placentals. Therefore, in evolutionary terms, this has become the most successful body structure and the most successful reproductive system among mammals in the last millions of years.