II SEM U5- MAMMALS BIOLOGY OF CHORDATES K HARISH BABU
side. Acrodont and pleurodont teeth lack roots, so
5.4 Dentition in Mammals nerves and blood vessels enter the pulp cavity at
Dentition refers to the structure, number, the base along the lateral side.
kind, and arrangement of teeth. The teeth of iii. Thecodont type: The dentition of animals in
mammals are the most highly specialized. which the teeth are set in deep sockets in the
Teeth serve the following functions jawbones. In mammals, the roots of thecodont
teeth are longer and they may be open or closed.
* Teeth are primarily used for grasping and
holding prey or food in the mouth cavity (buccal In open type, there is a wider opening in
cavity), the pulp cavity, which adds dentition throughout
life. Ex. incisors of rodents, tusks of elephants. In
* For chewing food, teeth are modified to act as a most cases, teeth are closed with a very small pulp
grinding mill. cavity that serves only to pass blood vessels and
* In addition, they function as tearing organs for nerves; such teeth do not grow after reaching a
offence and defence. specific size.
Toothless Mammals
Teeth are not present in all mammals. They are
absent in some monotremes, Echidnas, and
American anteaters. Platypus (Ornithorhynchus)
have horny epidermal plates instead of true teeth
in adulthood. The whalebone whale and many
edentates lack teeth only in adulthood.
Differentiation (Shape) of Teeth Succession of Teeth
Teeth can be classified morphologically into There are three types of teeth, depending on their
homodonts and heterodonts. permanence or replacement (succession):
1. Homodont Teeth: Most non-mammalian i. Polyphyodont: The dentition of animals in
vertebrates have teeth of the same type. Among which the teeth are continuously replaced
mammals, only certain cetaceans have homodont throughout life. This condition is not found in
dentition and have between 2 and 200 teeth. mammals.
2. Heterodont Teeth: Heterodont teeth are ii. Diphyodont: The dentition of animals with two
characteristic of mammals. This condition successions of teeth (milk teeth, permanent).
comprises incisors, canines, premolars, and Found in most mammals.
molars. They are dissimilar in shape, size and
iii. Monophyodont: The dentition of animals with
functions.
only one set of teeth throughout life. Ex. Platypus,
Attachment of Teeth Marsupials, Moles, Sirenians, Cetaceans
(toothless whales), etc.,
The manner of attachment of teeth at their bases
with the jawbones varies throughout the Significance of Teeth
vertebrates. These are of the following three types: * The dentition is so characteristic of mammals
i. Acrodont type: Teeth are attached on the crest that their classification is largely based on it.
or summit of the jawbone. Ex. Shark or Frog. Such Hence, studying dentition is important for
teeth are apt to break off easily but are replaced. understanding mammalian taxonomy.
ii. Pleurodont type: This condition occurs * The number of teeth present indicates the
commonly in Urodels and lizards. Teeth are approximate age of the mammal,
attached to the shelf-like indentations on the inner
* Study of dentition has helped determine the
margin of jawbone by their bases as well as one ancestry or pedigree of certain mammals.
PS Govt Degree College :: Penukonda :: Sri Satyasai Dt – 515110 U5-3
