Animal capable of walking or running on two legs in response to exceptional circumstances
A facultative biped is an animal that is capable of walking or running on two legs (bipedal), as a response to exceptional circumstances (facultative), while normally walking or running on four limbs or more.[1] In contrast, obligate bipedalism is where walking or running on two legs is the primary method of locomotion. Facultative bipedalism has been observed in several families of lizards and multiple species of primates, including sifakas, capuchin monkeys, baboons, gibbons, gorillas, bonobos and chimpanzees. Several dinosaur and other prehistoric archosaur species are facultative bipeds, most notably ornithopods and marginocephalians, with some recorded examples within sauropodomorpha. Different facultatively bipedal species employ different types of bipedalism corresponding to the varying reasons they have for engaging in facultative bipedalism. In primates, bipedalism is often associated with food gathering and transport.[2] In lizards, it has been debated whether bipedal locomotion is an advantage for speed and energy conservation or whether it is governed solely by the mechanics of the acceleration and lizard's center of mass.[3] Facultative bipedalism is often divided into high-speed (lizards)[4] and low-speed (gibbons),[5] but some species cannot be easily categorized into one of these two. Facultative bipedalism has also been observed in cockroaches[6] and some desert rodents.[7]
^Persons, W. Scott; Currie, Philip J. (2017). "The functional origin of dinosaur bipedalism: Cumulative evidence from bipedally inclined reptiles and disinclined mammals". Journal of Theoretical Biology. 420: 1–7. Bibcode:2017JThBi.420....1P. doi:10.1016/j.jtbi.2017.02.032. PMID 28254476.
^Hunt, Kevin D. (1996-02-01). "The postural feeding hypothesis: an ecological model for the evolution of bipedalism". South African Journal of Science. 92 (2): 77–90. hdl:10520/AJA00382353_7777.
^Clemente, C. J.; Withers, P. C.; Thompson, G.; Lloyd, D. (2008). "Why go bipedal? Locomotion and morphology in Australian agamid lizards". Journal of Experimental Biology. 211 (13): 2058–2065. doi:10.1242/jeb.018044. PMID 18552294.
^Schuett, Gordon W.; Reiserer, Randall S.; Earley, Ryan L. (2009). "The evolution of bipedal postures in varanoid lizards". Biological Journal of the Linnean Society. 97 (3): 652–663. doi:10.1111/j.1095-8312.2009.01227.x.
^Preuschoft, Holger (2004). "Mechanisms for the acquisition of habitual bipedality: Are there biomechanical reasons for the acquisition of upright bipedal posture?". Journal of Anatomy. 204 (5): 363–384. doi:10.1111/j.0021-8782.2004.00303.x. PMC 1571303. PMID 15198701.
^Alexander, R. McN. (2004). "Bipedal animals, and their differences from humans". Journal of Anatomy. 204 (5): 321–330. doi:10.1111/j.0021-8782.2004.00289.x. PMC 1571302. PMID 15198697.
^Russo, Gabrielle A.; Kirk, E. Christopher (2013). "Foramen magnum position in bipedal mammals". Journal of Human Evolution. 65 (5): 656–670. CiteSeerX 10.1.1.591.2458. doi:10.1016/j.jhevol.2013.07.007. PMID 24055116.
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exhaustive list of the forms of bipedalism, but most bipedal species use one or more of these techniques. Facultativebipedalism occurs in some species of antbears...
quadruped 'four feet'. Limited and exclusive bipedalism can offer a species several advantages. Bipedalism raises the head; this allows a greater field...
consistent with habitual bipedalism. However, recent postcranial evidence suggests characteristics consistent with habitual bipedalism and arboreal clambering...
have occasionally walked on its hind legs as a facultative biped. Other possible adaptations to bipedalism in Euparkeria include rows of osteoderms that...
Nonetheless, it remains a matter of controversy as to how bipedalism first emerged. The advantages of bipedalism were that it left the hands free to grasp objects...
Homo habilis, an advanced grasping-capable hand was accompanied by facultativebipedalism, possibly implying, assuming a co-opted evolutionary relationship...
supports the idea of a burrowing lifestyle. It is also proposed that facultativebipedalism occurred in Mesenosaurus. This is based on the presence of a rearward...
zeugopodium, or lower leg. This would have enabled facultativebipedalism in Prorotodactylus, and a wholly bipedal gait in later dinosauromorphs. Pace angulation...
danger or foraging), Protoceratops could have employed a rapid, facultativebipedalism. He also noted that the flat and wide pedal unguals of Protoceratops...
Protoceratops juveniles indicates that protoceratopsids were able to employ facultativebipedalism when young and became obligate quadrupeds in adulthood. However...
dictionary. As an adjective, obligate means "by necessity" (antonym facultative) and is used mainly in biology in phrases such as: Obligate aerobe, an...
mechanisms underpinning the evolutionary transition from obligatory or facultativebipedalism to an obligatory quadrupedalism in sauropodomorphs is published...
and the presence of her abductable hallux, that "Ardi" was a facultative biped: bipedal when moving on the ground, but quadrupedal when moving about in...
primitive features that include basally small sized bodies, obligate bipedalism, and simple teeth with one row in operation at a time that are replaced...
scelidosaur like animal walking in a bipedal manner, hinting that Scelidosaurus may have been more proficient at bipedalism than previously thought. The first...
and the ground pangolin commonly show an alternating bipedal gait. In humans, alternating bipedalism is characterized by a bobbing motion, which is due...
a neo-Lamarckian model of evolution to try and explain the origin of bipedalism. Neo-Lamarckism remained influential in biology until the 1940s when the...
J. Hooker) found from micro-CT scans that Anoplotherium being a facultativebipedal browser was not supported by the trabecular architecture of the proximal...
early archosauriforms walked on four limbs, euparkeriids were probably facultative bipeds that had the ability to walk on their hind limbs at times. The...
indicating that Huehuecuetzpalli mixtecus was bipedal while Tijubina pontei was facultativelybipedal. Augé, Dion & Phélizon (2021) describe the lizard...
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