Vertical clinging and leaping (VCL) is a type of arboreal locomotion seen most commonly among the strepsirrhine primates and haplorrhine tarsiers. The animal begins at rest with its torso upright and elbows fixed, with both hands clinging to a vertical support, such as the side of a tree or bamboo stalk. To move from one support to another, it pushes off from one vertical support with its hindlimbs, landing on another vertical support after an extended period of free flight. Vertical clinging and leaping primates have evolved a specialized anatomy to compensate for the physical implications of this form of locomotion. These key morphological specializations have been identified in prosimian fossils from as early as the Eocene. Vertical clinging and leaping primates Vertical clinging and leaping has only been observed in primates, and primarily in prosimians. A few anthropoids have been observed to engage in this behavior, such as Pithecia, and are similar in morphological adaptations to prosimians who rely on VCL. Vertical clinging and leaping strepsirrhine taxa include: Galagidae Indriidae Indri Propithecus Avahi Lepilemuridae (Lepilemur) Prolemur Cheirogaleus Vertical clinging and leaping haplorrhine taxa include: Tarsiidae Pitheciinae Cacajao Chiropotes Pithecia Cebuella Callimico Saguinus Variations in posture Variations in mid-flight posture The variations in vertical leaping can be classified into three types based on differences in mid-flight posture: (A) During the stretched-out vertical cling leap, the femur is extended. (ex. Indriidae) (B) During the curled-up vertical cling leap, the torso is sub-orthograde with all limbs positioned in front of the body. (ex. Galago) (C) During the limbs-down vertical cling leap, the torso is pronograde, with all limbs positioned underneath the body. (ex. Cheirogaleus) Variations in clinging posture There is an array of clinging postures that primates use while foraging and resting in trees. These postures include sitting, bipedal standing, squatting, forelimb suspension, forelimb-hindlimb suspension and more. Stabilization is key to how a primate positions themselves while clinging. The placement of the torso depends on the weight distribution between the hands, feet, and tail. Vertical clinging and leaping primates may also use their tails to grip adjacent branches in order to stabilize their positional modes. Morphological specializations Locomotion and movement are the main contributing factors to primate's body shape and structure, thus the anatomy of vertical climbers and leapers is highly specialized to enable them to move effectively within their arboreal habitat. Features found in the hips, knees, feet, hands, arms, and