ESS261H1 Lecture Notes - Lecture 11: Squamosal Bone, Synapsid, Stapes
Document Summary
Today we will map out evolution from the cambrian period to present day. Spinal notochord and muscle development during cambrian e. g. The jaw evolved during the ordovician (from slits to gills) Armoured fish w/ jaw bones & hinged head shield during sil-it dev. Teeth since dev (e. g. sharks and rays) Bony fish since dev (e. g. ray finned, lobe finned: tetrapods (are four-footed animals, lobe-finned fish developed lungs & moved on land in dev. Acanthostega is the transitional form between fishes" and tetrapods". Fish features: gill-bars, no true elbow, knees, wrists, ankles (not weight-bearing, long fin rays around tals. Tetrapod features: head not foined to shoulder girdle, ear bone (stapes) fits into fenestra, ovails/vestibule are in braincase, large pelvic girdle, sacral rib. February 25, 2015: femur as large as humerus, tibia and gibula attached to ankle bones, digits on each limb, amniotes developed in it carb.
