BIOL-3030 Lecture Notes - Lecture 22: Arrector Pili Muscle, Morganucodon, Epiphyseal Plate
Document Summary
Modern mammals modify harderian gland near eye to issue secretions spread (by paws) over fur. Duct for gland has typical shape in mammals, seen in skull. Duct shape found in morganucodon and megazostrodon, so they had fur and were among the first mammals. Precisely occluding (fitting together) cheek teeth divided into premolars and molars (heterodont dentition) Only one set of replacement teeth = diphydonty (some teeth only in adult) Enlarged brain capacity (mostly hearing and smell - possibly nocturnal?) Earliest mammals mostly tiny, but some larger baby dino killers. Middle ear bones, derived from ancestral jaw bones. This means that only the lower jaw bone in mammals is the dentary (aids withstanding forces of complicated mammalian jaw movements) Dentary = single jaw bone bearing teeth in bottom of mouth. Epiphyses and cartilage growth plates: determinate growth. Growth plate - dark line, where bone replaces cartilage. Epiphyses - bone capping growth plate, fuses to shaft to end growth.
