palaeontologists have found some exceptional places (lagerstätten) where fossils of early birds are found. the preservation is so good that on the best examples impressions of their feathers can be seen, and sometimes even the remains of meals they have eaten. from these remains we know that birds evolved from small carnivorous dinosaurs (theropods) in the jurassic period. they radiated into a huge variety in the lower cretaceous. at the same time, their direct competitors, the pterosaurs, dwindled in numbers and variety, and became extinct at the end of the mesozoic.