BIO 357 Lecture Notes - Lecture 10: Axial Skeleton, Neural Crest, Ulna
Document Summary
Thus, it is important that the type of motion is limited at desired times. Pectoral limbs may have come from an extended gill ray. There is an issue with this though. The skeletal system isn"t from neural crest, but gill arches are. Fin folds on amphioxus may have broken up to become modern fins. Lepidotrichia- supporting elements for the rays at the end of the fins. The humerus, radius, and ulna began in these fins. Still seen some today, even in humans. Allow the appendages to attach to the axial skeleton. Basal elements develop and strengthen into the girdle. A number of bones went into the early pectoral girdles in fish. Some of these are lost in amphibians. In mammals, coracoid joins with the more dominant scapula. The pectoral attachment to the skull is loss. One bone in fish became three pelvic bones today- ilium, ischium, and pubis. The long ilium extends the mammalian, increasing the animal"s speed.
