Final answer:
On land, the large meat- and plant-eaters of the Early and Middle Jurassic were dinosaurs. Dinosaurs were the dominant terrestrial vertebrates during this period and showed tremendous diversity in form and function.Thus the correct option is D.
Step-by-step explanation:
On land, the large meat- and plant-eaters of the Early and Middle Jurassic were dinosaurs. During this time period, dinosaurs became increasingly important and were the dominant terrestrial vertebrates which filled most ecological niches. This is reflected in the fossil record which shows a tremendous diversity of dinosaur species that existed, ranging from the massive, plant-eating sauropods to the fierce carnivorous theropods. These dinosaurs laid eggs and had evolved various adaptations such as bipedal or quadrupedal locomotion, different types of teeth for various diets, and complex behaviors that may have included parental care.
The other options - rauisuchians, phytosaurs, and metoposaurs - were not the dominant large land vertebrates during the Early and Middle Jurassic, although they did exist in earlier periods or had different ecological roles.