陨石撞击地球之前恐龙数量已经在下降

Dinosaurs ¹ were already in an evolutionary ³ decline tens of millions of years before the meteorite ⁴ impact that finally finished them off, new research has found. The findings provide a revolution in the understanding of dinosaur ² evolution. Palaeontologists previously ⁵ thought that dinosaurs were flourishing right up until they were wiped out by a massive meteorite impact 66 million years ago. By using a sophisticated statistical ⁶ analysis in conjunction with information from the fossil record, researchers at the Universities of Reading, UK and Bristol, UK showed that dinosaur species were going extinct at a faster pace than new ones were emerging from 50 million years before the meteorite hit. , ,he analyses demonstrate that while the decline in species numbers over time was effectively ubiquitous among all dinosaur groups, their patterns of species loss were different. For instance, the long-necked giant sauropod dinosaurs were in the fastest decline, whereas theropods, the group of dinosaurs that include the iconic Tyrannosaurus rex, were in a more gradual decline., ,Dr Manabu Sakamoto, University of Reading, the palaeontologist who led the research, said: "We were not expecting this result. While the asteroid ⁷ impact is still the prime candidate for the dinosaurs' final disappearance ⁸, it is clear that they were already past their prime in an evolutionary sense."