Lect. 10 Masticatory Apparatus
y
y
y
Teeth
Jaws
Muscles
•Behavior
•Life history
•Diet
•Phylogeny
1
Reptiles vs. Mammals
2
Muscles of Head
y
y
y
y
Temporalis
Medial pterygoid
Masseter
Lateral pterygoid
3
1
Muscles of Mastication
4
Skull Architecture
Supraorbital
torus
Sagittal
Crest
Nuchal
Crest
5
Mandible as Lever
y
y
y
Load arm
Power arm (Effort)
Fulcrum
SIMIAN SHELF
MANDIBULAR TORUS
HUMAN CHIN
6
2
Evolutionary Trends
Tarsier
7
Homodont/Heterodont
Homodont/
Heterodont Teeth
Reptile vs. Mammal
8
Ancestral Mammal
y
y
y
Dental formula:
3.1.4.3
3.1.4.3
9
3
Primate Teeth
Catarrhine
Platyrrhine
10
Incisors
Spatulate
human
ape
Tooth comb
11
Canines
Conical & pointed
Sectorial condition
Canine diastema
12
4
Premolars (bicuspids)
Apes and monkeys
human
13
Molars
OW Monkey
Human
Bilophodont condition
14
Early Hominin Dentition
A. afarensis
ape
p
First premolar
One cusp
human
intermediate
Two cusps
15
5
Features of Teeth
16
Chimp/Hominin
Chimp/
Hominin
Humans:
Parabolic arcade
I not enlarged
C small
Lower 1st PM not sectorial
Molars bulbous
Y-5 to +4 molar cusps
17
Tooth Eruption Patterns
Ape: M1 →I1 →I2→M2→ P3→ P4→ C→ M3
Human: M1→I1→I2→P3→ C→P4→M2→ M3
y M = molar, I = incisor, P = premolar and C =
canine.
y
y
Taung: Australopitheucs africanus
Turkana Boy: Homo erectus
18
6
Dental Studies
y
y
y
y
y
y
Tomography (CT)
Striae of Retzius
Toothwear
Patterns
Phytolyths
Enamel Thickness
Ardipithecus
ramidus
Timothy Bromage &
Christopher Dean
19
Rates of Maturation in Hominins
Bromage and Dean
20
Enamel Thickness
Modern human: thick enamel
African apes: thin enamel
F il hominins:
Fossil
h i i thick
thi k
Exception: Ardipithecus ramidus
Common ancestor of African hominoids: thin enamel
21
7
Tooth wear patterns
Scanning electron microscope (SEM)
Grazers: etched w/fine lines
Browsers & fruit eaters: smooth worn
Scavengers: deeply marked
Homo erectus: pitted
i d andd scratched
h d enamell
22
8