G404 Geobiology
Jaws and teeth
Structure, Function and Diet
Reading: Benton Chapter 10
(to p. 311)
Teleoceras upper P4
and M1 (P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Structures associated with jaw movements in mammals
Zygomatic Arch: composed
Temporal Fossa: area for
of the jugal (or zygomatic)
muscle attachment and
and squamosal bones,
movement of the mandible,
muscle attachment along
site of muscle attachment
lower margin
Coronoid process of the mandible:
site of muscle attachment
Joint: condyle of the mandible fits
into the glenoid fossa of the
squamosal (note same name as
glenoid fossa of the pectoral girdle)
Angular process of the mandible:
site of muscle attachment Masseteric fossa of the mandible: Dog skull (P. David Polly)
site of muscle attachment
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Muscles that move the mandible
Temporalis - originates on the side of the
braincase, inserts on the coronoid process,
pulls the mandible upward and backward. Temporalis
Masseter - originates on the zygomatic arch,
inserts in the masseteric fossa and on the
lateral angle of the mandible, pulls the
mandible upward, laterally, and forward.
Pterygoideus - originates on the pterygoid
plates, inserts on the medial angle of the
mandible, pulls the mandible upward,
medially, and forward.
Masseter
Pterygoideus
(Evans, Miller’s Anatomy of the Dog)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Muscle action to elevate (close) the mammalian mandible
Tem
pora
lis
er
et
ass
M
Dog skull (P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Dorsal and medio-lateral action of the muscles
temporalis
masseter pterygoideus
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Animated model of teeth in action
Note how tall trigonid of lower molars passes
between upper teeth and how the protocone
of the upper molars slides across low talonid
basin of lowers in mortar-and-pestle fashion
Model by Alistair Evans, Monash University
http://users.monash.edu.au/~arevans/3d.html
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Vertebrate dietary categories
Omnivore - mixed diet
Frugivore - diet
Herbivore - generalized specializing on fruits (only
diet on plant leaves and exists after the
stems Cretaceous)
Granivore - diet
Piscivore - carnivorous diet
specializing on seeds and
specializing on fish
nuts
Insectivore - diet
specializing on insects
(and sometimes other Carnivore - generalized diet
invertebrates, like of flesh and fat
worms)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Metabolic rate and body size
Log metabolic rate (O2/hr/g)
1.50
1.00
0.50
0.00
-0.50
-1.00
-1.50
-4.0 -2.0 0.0 2.0 4.0
Log body mass (kg) Data from Eisenberg, 1981
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Energy value in different food sources
Small animals = high metabolic rate = high calorie diet = small animals must be insectivores and granivores
Large animals = lower metabolic rate = lower calorie diet = large animals can be herbivores and frugivores
700
525
kcal per 100 g
350
175
0
Insects Nuts and Seeds Meat and Fat Fruits Leaves and Grasses
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Dentition of the dog, Canis familiaris
Carnivore to omnivore
First upper Last upper
molar (M1) premolar (P4)
First lower
molar (M1)
Last lower (P. David Polly)
Department of Geological Sciences | Indiana University
premolar (P4) (c) 2011, P. David Polly
G404 Geobiology
Dentition of the dog, Canis familiaris
Carnivore to omnivore
nipping
slicing or and biting
shearing
(carnassial)
chewing or tearing and
crushing gnawing
(P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Muscle attachment points in a leopard, Panthera pardus
Carnivore
temporalis
masseter
(P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Carnassial of a leopard, Panthera pardus
Specialized pair of teeth in
mammalian carnivores for
slicing
Carnassial composed of upper
P4 and lower m1 in Order
Carnivora
Leopard, Panthera pardus, carnassial (P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Muscle attachment points in an elk, Cervus elaphus
Herbivore
temporalis
(P. David Polly)
masseter
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Mandible of an elk, Cervus elaphus
Herbivore
grinding cropping
(P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Upper molars and premolars of a horse, Equus caballus
Herbivore
Enamel Dentine
Cement
(P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Mandible of a wild boar, Sus scrofa
Omnivore
tearing
grinding biting
(P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Muscle attachment points on a wild boar, Sus scrofa
Omnivore temporalis
masseter
(P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Mandible of a rat, Rattus rattus
Granivore to omnivore
grinding gnawing
(P. David Polly)
incisor root
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Mandible of a shrew, Blarina brevicauda
Insectivore
puncturing
and crushing grasping
(P. David Polly)
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Joint and tooth rows in shearing dominated
versus grinding dominated
Carnivore
Shearing dominated
Herbivore
Grinding dominated
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Mandibular condyle shape in shearing
dominated versus grinding dominated
(P. David Polly)
Omnivore
Carnivore Grinding dominated
Shearing dominated
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Summary of mammalian dietary specializations
Insectivores small body size; sharp dentition for puncturing and crushing; large
temporalis muscle; cylindrical condyle
Granivores small body size; ever-growing incisors, grinding molars and
premolars; large masseter muscle; dual-action condyle
Carnivores medium body size; large canines; shearing-dominated dentition
often with carnassial; large temporalis; cylindrical condyle; joint level with
tooth row
Herbivores medium to large body size; grinding-dominated dentition; cropping
incisors; large masseter and pterygoideus; rounded condyle; joint above tooth
row
Omnivores medium to large body size; grinding-dominated dentition but with
rounded, puncturing cusps; large masseter and pterygoideus; rounded
condyle; joint above tooth row
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly
G404 Geobiology
Scientific papers for further reading
Bown, T.M. and M.J. Kraus. 1979. Origin of the tribosphenic molar and metatherian and
eutherian dental formulae. Pp. 172-181 in J.A. Lillegraven, Z. Kielan-Jaworowska and W.A.
Clemens (eds), Mesozoic Mammals: The First Two-Thirds of Mammalian History. University of
California Press: Berkeley, California.
Crompton, A.W. and P. Parker. 1978. Evolution of the mammalian masticatory apparatus.
American Scientist, 66: 192-201.
Evans, A.R., G.P. Wilson, M. Fortelius, and J. Jernvall. 2007. High-level similarity of dentitions
in carnivorans and rodents. Nature, 445: 78-81.
Polly, P.D., S.C. Le Comber, and T.M. Burland. 2005. On the occlusal fit of tribosphenic molars:
Are we underestimating species diversity in the Mesozoic? Journal of Mammalian Evolution,
12: 285-301.
Department of Geological Sciences | Indiana University (c) 2011, P. David Polly