ZOO 2090 Lecture Notes - Lecture 14: Mandible, Haemal Arch, Middle Ear
23 Nov 2016
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Day 14: jaw articulation and mammalian middle ear bones. Evolved from 1st and 2nd branchial arches. 3. hyomandibula - became the first early bone (columella) in amphibians/reptiles - stapes. All mammals have 7 cervical vertebrae, best at rotation. 2. best atlas-axis rotation thoracic: ribs lumbar: no ribs sacral: articulate with pelvic girdle caudal: presence of hemal arch. Many modifications of the girdles and limbs. **talked a bit about the collarbone, and how cats don"t have one so they can fall long distances and stuff. Plantigrade = whole foot touches the ground [humans] Digitigrade = just the toes/digits touch the ground [dogs] Unguligrade = just the fingertips" touch the ground [deer, horses] Probably not! temporal pattern: successive diversifications, or episodes of quick splitting of relatively short-lived clades. Now strong evidence for ecological specializations transformation of key innovations: Not quite incremental assembly of complex features", many precursory experiments. Modern representatives are the platypus, and echidnas (a few species of spiny anteaters)
