THIS year our furry ancestors came snarling out of the undergrowth, their teeth bared. Until now, mammals in the Cretaceous had been portrayed as shivering insectivores skulking in the shadows of the mighty dinosaurs. But no longer. It was payback time, and dinosaur was on the menu.
Our preconceptions were overturned by the discovery of two stunning mammal fossils. Repenomamus giganticus, at a metre long, the bigger of the two, had fearsome teeth similar to a modern Tasmanian devil and was big enough to hunt small dinosaurs. Even the smaller Repenomamus robustus was no timid shrew: the bones of a young psittacosaurus (a common bipedal plant-eater) were found in its stomach, indicating that the mammal gulped down chunks torn from its prey.
The fossils were found in Lianoning province, an area of north China famed for its feathered dinosaurs, in rocks dated to 130 million years ago 鈥� pushing back by a full 65 million years the date at which mammals that big were thought to have been around. Our ancestors clearly did not have to wait for the extinction of the dinosaurs before evolving a larger body and a more predatory lifestyle. There is much we still have to learn about those early mammals.
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The two Repenomamus species, however, weren鈥檛 so tough that they survived the Cretaceous. No fossils of triconodonts, the subclass of mammals to which the fearsome fossils belonged, have been found after that time. They may have gone extinct before the dinosaurs, but their fossils have definitely given the mammalian image a thorough makeover.
And here are all of New Scientist鈥檚 roundup stories for 2005.
