Final answer:
The statement that hadrosaurids may have contributed to the decline of hypsilophodontids and iguanodontids is false. While these dinosaur groups coexisted, the decline of dinosaur species is attributed to major global events like the end-Cretaceous mass extinction rather than interspecific competition.
Step-by-step explanation:
It is false that hadrosaurids may have contributed to the decline of hypsilophodontids and iguanodontids. The rise and fall of various dinosaur groups like hadrosaurids, hypsilophodontids, and iguanodontids are complex and influenced by a multitude of ecological and evolutionary factors. Dinosaurs from different groups often occupied various ecological niches and experienced their own unique evolutionary trajectories.
Hadrosaurids, commonly known as duck-billed dinosaurs, reigned during the Late Cretaceous period. Their success and diversification are unlikely to be the sole cause of the decline in other ornithischian dinosaurs, such as hypsilophodontids and iguanodontids. These groups had different lifestyles and may not have been in direct competition. The end-Cretaceous mass extinction event significantly impacted all dinosaur groups, not selective competition among them.
Understanding these dynamics requires a broad look at the fossil record and environmental changes over time. Various factors like drastic climate shifts, volcanic activity, and asteroid impacts have been more consequential for the dinosaur extinction at the close of the Mesozoic Era.