Pendular motion in the brachiation of captiveLagothrix andAteles

Three‐Legged Locomotion and the Constraints on Limb Number: Why Tripeds Don’t Have a Leg to Stand On

“…[49,53] Perhaps ambipedal progression, then, should actually be considered a form of pentapedalism. Howler, spider, and wooly monkeys use their tails to navigate, ascend, and descend through tree branches, [56][57][58][59][60][61][62] employing various forms of locomotion called tail-arm suspension [63] and tail-assisted brachiation. [54] In many primates, the tail functions as the third appendage during tripedalism either for enhancing locomotion that would otherwise be bipedalism or to free up other appendages for activities such as carrying objects.…”

“…[55] An excellent example of this is the prehensile tail use in various primate groups. Howler, spider, and wooly monkeys use their tails to navigate, ascend, and descend through tree branches, [56][57][58][59][60][61][62] employing various forms of locomotion called tail-arm suspension [63] and tail-assisted brachiation. [64] Use of the tail may function to spread the animal's weight over more supports, allowing them to traverse smaller branches and access resources inaccessible to other, similarly sized primates.…”

One step beyond: Different step-to-step transitions exist during continuous contact brachiation in siamangs

“…This lifting of the bCOM can contribute to the pendular momentum, especially combined with release timing of the trailing hand at the highest point. Turnquist et al (Turnquist et al, 1999) also observed this lifting of the bCOM by trailing elbow flexion during brachiation of woolley monkeys ( Lagothrix lagotricha) , while spider monkeys ( Ateles fusciceps) attain the same by using their tail (Turnquist et al, 1999). Jungers and Stern (Jungers and Stern, 1981) also described trailing elbow flexion in gibbon brachiation, although without indicating whether this was associated with a loop transition.…”

African apes and the evolutionary history of orthogrady and bipedalism

“…Following Owen (1859), Keith (1899, p. 305) defined brachiation as “use of the arms as one of the main organs of locomotion,” which Gregory (1916, p. 333) later specified as “swinging from branch to branch with the arms.” Avis (1962, p. 135) further refined brachiation as a particular set of movements employed during bimanual progression: “The gibbon has compensated for its relatively small body size by developing elbow flexion and humeral retraction to bring arm‐swinging to its maximum speed.” Avis (1962, p. 135) also argued that gibbons (hylobatids) differ from great apes (hominids) in a limited sense: “The larger apes have capitalized on trunk rotation and forearm supination, movements which enable them to lift their heavier bodies relatively great distances even among flimsy supporting structures.” Slower speed brachiation similar to that of great apes is also used by hylobatids, especially by the larger‐bodied siamangs ( Symphalangus syndactylus ) (Fleagle, 1974, 1976). Further, brachiation is now recognized outside of Hominoidea, including in an odd‐nosed colobine monkey (Bailey et al, 2020; Byron & Covert, 2004; Su & Jablonski, 2009; Wright et al, 2008) and as a tail‐assisted form in atelines (spider monkeys and close relatives) (Cant et al, 2003; Turnquist et al, 1999; Youlatos, 2002). Brachiation, therefore, should be qualified when used in the literature (e.g., high‐speed brachiation, tail‐assisted brachiation, etc.)…”

“…Slower speed brachiation similar to that of great apes is also used by hylobatids, especially by the larger-bodied siamangs (Symphalangus syndactylus) (Fleagle, 1974(Fleagle, , 1976. Further, brachiation is now recognized outside of Hominoidea, including in an odd-nosed colobine monkey (Bailey et al, 2020;Byron & Covert, 2004;Su & Jablonski, 2009;Wright et al, 2008) and as a tail-assisted form in atelines (spider monkeys and close relatives) (Cant et al, 2003;Turnquist et al, 1999;Youlatos, 2002). Brachiation, therefore, should be qualified when used in the literature (e.g., high-speed brachiation, tailassisted brachiation, etc.)…”