From the greenhouse to the cold store - mammals in the shadow of the dinosaurs

The undisputed rulers of the Mesozoic era were the dinosaurs, which lived on all continents in an impressive variety of forms and are among the largest land vertebrates of all time. In contrast, the mammals of the Mesozoic were long regarded as primitive, shrew-like creatures that eked out an inconspicuous existence in the shadow of the dinosaurs. This view has changed fundamentally over the past 20 years. New spectacular finds from China and Mongolia, but also from Europe, have shown that the mammals displayed an astonishing ecomorphological diversity even at the beginning of their careers. Early representatives of long-extinct branches of the mammalian family tree were already highly specialised and dug like moles in the jungle floor, swam like otters in the water or glided from tree to tree. Their tiny body size compared to the dinosaurs forced the early mammals to lead a crepuscular lifestyle. Their high metabolism, coupled with their warm-bloodedness, and their good sense of hearing (for detecting insects) were a great advantage. Ultimately, it was these tiny creatures that triumphed over the giants of the Mesozoic era when the Earth was devastated by an asteroid impact 66 million years ago. The sun was eclipsed for centuries by dust and aerosols hurled into the atmosphere, leading to a drastic cooling of the climate. Now it was the mammals' turn, as their small size and warm-bloodedness were an invaluable advantage during this impact winter, while the dinosaurs died out. After a few million years, the mammals had conquered their habitats, with large herbivores and predators. The foundations for this unprecedented success story, which continues to this day, were laid in the greenhouse climate of the Mesozoic era.