. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 194 ANNALS OF THE SOUTH AFRICAN MUSEUM body weight to this new base and its epipodial pillar. Then follows a horizontal rotation of the femur about the knee, atop the more or less fixed epipodials, which moves the acetabulum forward. At the same time the body weight is held above the ground, or at least lifted enough to be slid forward. The mecha- nics are first to lift and swing the epipodium and foot forward, then to reverse the forces and lift the body on this new fulcrum and propel the body forwa
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 194 ANNALS OF THE SOUTH AFRICAN MUSEUM body weight to this new base and its epipodial pillar. Then follows a horizontal rotation of the femur about the knee, atop the more or less fixed epipodials, which moves the acetabulum forward. At the same time the body weight is held above the ground, or at least lifted enough to be slid forward. The mecha- nics are first to lift and swing the epipodium and foot forward, then to reverse the forces and lift the body on this new fulcrum and propel the body forward. As described by Schaeffer (1941: 412) in the salamanders, the propulsion phase begins immediately on the contact of the plantar surface of the foot with the ground. The recovery phase starts with the dorsal surface of the foot turning laterally into a vertical position. The crus is carried forward as an extension of the femur until just in front of a position at right angles to the body. The last movements involve a flexion of the knee, the extension of the foot and its rotation into a horizontal plane. This kind of limb movement, Schaeffer noted, was probably used by the smaller primitive amphibians. He went on to point out that Gregory & Camp (1918) had described the Permian reptile knee as permanently bent, and he thought that the heavier labyrinthodonts must have had similarly permanently flexed knees. Broom (1921) presented the first general review of the reptilian tarsus, tracing it from the early Permian labyrinthodont Trematops milleri up into the therapsid reptiles. While he did include some other reptiles, he did not discuss the thecodonts or the dinosaurs. He noted Gegenbaur's pioneer work and used his terminology. Schaeffer (1941) also began with the tarsus of Trematops. From this he derived that represented by the early Permian cotylosaur Labidosaurus, and this became the ancestral pattern for later tetrapods. He found these later forms to have three diverg
Size: 1455px × 1718px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
