London: The same asteroid that killed the dinosaurs in the Cretaceous period 66 million years ago also wiped out over 90 per cent of mammal species, significantly more than previously thought, new research has found. Following the asteroid hit, most of the plants and animals would have died, so the survivors probably fed on insects eating dead plants and animals. With so little food, only small species survived. The biggest animals to survive on land would have been no larger than a cat, the study said. For the study, the researchers reviewed all mammal species known from the end of the Cretaceous period in North America. Their results showed that over 93 per cent became extinct across the Cretaceous-Paleogene (K-Pg) boundary, but that they also recovered far more quickly than previously thought. The scientists analysed the published fossil record from western North America from two million years before the Cretaceous-Paleogene boundary, until 300,000 years after the asteroid hit. They compared species diversity before and after this extinction event to estimate the severity of the event and how quickly the mammals recovered. "The species that are most vulnerable to extinction are the rare ones, and because they are rare, their fossils are less likely to be found. The species that tend to survive are more common, so we tend to find them,” said one of the researchers Nick Longrich from Milner Centre for Evolution in the University of Bath in England. "The fossil record is biased in favour of the species that survived. As bad as things looked before, including more data shows the extinction was more severe than previously believed," Longrich noted. The researchers said this explains why the severity of the extinction event was previously underestimated. The study was published in the Journal of Evolutionary Biology.