Final answer:
Arctometatarsalians and Maniraptora are two different groups of dinosaurs. Arctometatarsalians have a specialized foot structure, while Maniraptora have long arms and feathers.
Step-by-step explanation:
Arctometatarsalians and Maniraptora are two different groups of dinosaurs belonging to the clade Theropoda. Arctometatarsalians are characterized by having a specialized foot structure, where the third metatarsal bone is pinched between the second and fourth metatarsals. This unique adaptation is not found in Maniraptora.
On the other hand, Maniraptora is a subgroup of theropod dinosaurs that includes birds and their closest relatives. They are characterized by having long arms, a wishbone, and feathers. Unlike Arctometatarsalians, Maniraptora does not have the specialized foot structure.