Any South American monkey (platyrrhine) species in either of two families: marmosets (Callitrichidae) or South American monkeys other than marmosets (Cebidae), including capuchins and spider monkeys.
One of the hallmarks of being a hominid is having opposable thumbs: stronger, longer and more flexible than the thumbless hands of a spider monkey or the non-opposable thumbs of a marmoset.
At least not internally, spider monkeys have been observed pulling back a branch hand over hand using multiple muscle strokes stored in the bend of the branch to catapult themselves forward.