Complex sentence: A quick and agile runner with strong legs, "Dryosaurus" used its tail as a counter-balance, while making sharp turns and probably relied on its speed as a main defense against carnivorous dinosaurs.
Split into simpler sentences: A quick and agile runner with strong legs, "Dryosaurus" used its tail as a counter-balance. It probably relied on its speed as a main defense against carnivorous dinosaurs.