Final answer:
The claim that Rhabdodonts and Dryosaurs were quadrupedal due to short arms is false, as both dinosaur groups were bipedal and likely used their long tails for balance, counteracting the weight of their long necks.
Step-by-step explanation:
The statement 'Rhabdodonts and Dryosaurs had short arms which meant they were quadrupedal' is false. Rhabdodonts were generally considered to be bipedal herbivores; they are characterized by having hind limbs that were longer and stronger than their forelimbs, suggesting they moved primarily on two legs. Similarly, Dryosaurs were small, fast-moving dinosaurs that were also believed to be bipedal due to their long hind legs and short arms, adapted for running.
As for why bipedal dinosaurs with long necks invariably had long tails, one logical reason is balance. A long tail would counterbalance the weight of a long neck, helping these creatures maintain their centre of gravity and remain stable while walking or running on two legs.