The end-Cretaceous mass extinction

Around 75 per cent of species vanish at the Cretaceous-Paleogene boundary. The non-avian dinosaurs go entirely, along with the pterosaurs, mosasaurs, plesiosaurs, ammonites, rudists and most planktonic foraminifera. Survival is strongly biased: small body size, generalist diets, freshwater habitats and the ability to burrow or lie dormant all help, which is why crocodiles, turtles, mammals, birds and insects come through. The Alvarez iridium anomaly proposed the impact cause in 1980, against decades of resistance; the crater's discovery a decade later largely settled it. The ecological ceiling that had held mammals small for 160 million years is removed in an afternoon.