ADAPTATIONS FOR BIPEDAL LOCOMOTION OF LIZARDS
1962; Oxford University Press; Volume: 2; Issue: 2 Linguagem: Inglês
10.1093/icb/2.2.191
ISSN2162-4445
Autores Tópico(s)Primate Behavior and Ecology
ResumoIn the course of vertebrate history, four rather distinct types of bipedalism have evolved: (1) the reptilian method (thecodonts, dinosaurs, lizards) in which the body is balanced more or less horizontally over the legs and the tail acts as a cantilever; (2) the avian method in which, with obvious exceptions, the body is balanced horizontal? ly over the legs and the center of gravity is directly over the hindlimbs; (3) the primate-human method in which the body is balanced semi-vertically or vertically over the limbs; and (4) the ricochetal method of saltatorial mammals in which the body is also balanced semi-vertically and the highly modified hindlegs are used simultaneously in repetitive jumping. Bipedal locomotion has thus evolved independently at least six times in vertebrate phylogeny; twice in reptiles (thecodont-dinosaur group, lizards), once in birds, and three times in mammals (marsupial ricochet, placental ricochet, primate alternating gait). It is of course recognized that several other kinds of mammals can attain a degree of bipedal? ism for short periods, but in none of them is the position maintained, nor the gait habitually used. With the exception of several species of lizards (Snyder, 1952), most birds, and man, no other living vertebrate regularly progresses at the bipedal two-time gait. As Howell (1944) has pointed out, the bipedal walk and run has, except for birds, developed from quadrupedal methods of loco? motion and he has briefly discussed some
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