Basic Terms Used for Feeding Mechanisms of Vertebrates 1. Suspension-feeding (= filter-feeding) - filter small particles (alive or dead, depending on species) out of water column 2. Suction-feeding - open mouth, suck in food 3. Ram-feeding - open mouth, swim over food Ram-Suction Index - compares movement of food relative to movement of feeder 4. Inertial-feeding - inertia of food is used to move it in oral cavity 5. Transport - movement of food within oral cavity (by water currents in aquatic vertebrates or tongue in tetrapods) 6. Mastication - physical reduction of food size by chewing
Wear Patterns of Teeth are Functionally Important Enamel is > 95% inorganic matter; it is the hardest substance in vertebrate bodies Enamel is harder than dentine Dentine is harder than cement These properties mean that teeth can be self-sharpening
Some Important Terms for Teeth Polyphyodont - multiple generations of tooth replacement (most vertebrates) Diphyodont - two sets of teeth: milk and permanent (most mammals; incisor, canine and premolar teeth are replaced) Monophyodont - a single set of teeth (e.g., cetaceans) Homodont - teeth of similar shape along jaw Heterodont - teeth of different shape along the jaw Tooth plate or Toothplate - at least two uses are common: 1. Many individual teeth fused together at their bases; separate cusps are still visible (e.g., in pharynx of fishes) 2. Fusion of individual teeth during ontogeny: separate cusps may not still be visible (e.g., lungfishes, chimaeras)
Types of Mammalian Teeth and Dental Formulae Incisor teeth (I), typically these are replaced Canine teeth (C), typically these are replaced Premolar teeth (P), typically these are replaced Molar teeth (M), typically these are not replaced Formulae are expressed as type # in upper jaw/# in lower jaw I 5/4, C 1/1, P 2/2, M 4/4 = opossum I 2/2, C 1/1, P 2/2, M 3/3 = humans
Terms for Mammalian Molars Tribosphenic molars - plesiomorphic condition seen in opossums and insectivores Bunodont molars - low-crowned condition seen in omnivores such as humans and pigs Lophodont molars (e.g., Rhinoceros, Fig. 16-9A) Selenodont molars (e.g., deer, Fig. 16-9B). Molarization of premolars (remember that premolars are replaced wheras molars are not replaced.) High-crowned, or hypsodont, molars (e.g., horse, Fig. 16 -9C).