Variety in teeth form was one indication of their relatedness to mammals. Mammalian skin has epidermal and dermal layers and the unique keratinized derivative of hair seated in epidermally-derived hair follicles. While hair is usually for insulation, it may also be for sense, e.g. the vibrissae or whiskers. Horns have a bony core. Antlers are all bone without a covering of keratin, but unlike horns, are shed every year.
Mammalian teeth are highly variable or heterodont .
A diastema is a gap between the anterior and posterior teeth, allowing for an elongated snout, e.g., in deer. Muscles attach at an origin and an insertion , and produce an action . 1,3 Digestive system . Will discuss more next week. Sheep and cattle are ruminants with specialized four-chamber stomachs that also function as fermentation pouches to digest the cellulose in plants.