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.
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.
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.
Rainbow-colored macaws and harpy eagles fly overhead while three-toed sloths hang by their feet, spider monkeys jump from branch to branch, and huge snakes hang from tree limbs.
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.