One interesting idea put forward in 1962 supposes that the evolution of those flowering plants was followed by the first appearance of the butterflies and moths… The caterpillars of butterflies and moths feed almost entirely on plants: today their numbers are kept down by natural enemies, notably birds, but when the caterpillars first appeared on the scene the birds had not yet realized how good they were to eat. For some time, therefore, the caterpillar population increased without check. They ate so much plant food that none remained for the plant-eating dinosaurs; the plant-eating dinosaurs died of starvation, and so the meat-eating dinosaurs which preyed on them also without food.
Alan Charig, A New Look At The Dinosaurs, Facts on File, N.Y., March 1983, p.150-1.
Alan Charig was a leading paleontologist at the Natural Histoty Museum, London