There is evidence that dinosaurs did not have a single, uniform and universal diet but rather a wide variety of dietary habits, with evidence supporting the idea that carnivorous, herbivorous and omnivorous species all existed. Different feeding styles were also likely, with some carnivorous species hunting prey such as mammals and small reptiles, while other carnivores may have been opportunistic carrion scavengers. There was likely even a good range of dietary variety amongst the herbivorous dinosaurs, which may have made up the majority of all dinosaur species.
Dinosaurs lived on earth for more than 130 million years, and during this time, the planet underwent some dramatic changes that may have influenced dinosaur diet. For example, later herbivorous dinosaurs are believed to have fed on flowering plants that produced fruit, while earlier species of herbivores may have focused more on conifer trees, mosses and ferns.
The fossil record shows that even smaller groups of dinosaurs, such as the theropods, may have displayed a wide variety of dietary preferences among different species, making it even harder to characterize a single dinosaur diet. Additionally, scientists have been unable to determine what some dinosaurs, such as the toothless Oviraptorosauria, might have eaten.