Characteristics of Class Mammalia are given below:
1) Warm blooded.
2) Possess hair which is made of keratin. The evolution of mammalian keratin is believed to be independent of reptilian keratin. Hair provides insulation .
3) Endothermic. The majority of the heat energy is used to maintain their high body temperature.
4) Four chambered heart.
5) Mammary glands are used to produce milk to nourish their young. Female glands are the only functional glands.
6) Thediaphragm is a muscle that separates the thoracic cavity from the abdominal cavity.
7) Seven cervical vertebrae (neck bones) are present in most mammals.
8) Most are viviparous though some are oviparous. An extended gestation period uterine development is common in most placental mammals.
9) Teeth are imbedded in the jaw bone and come in a variety of forms.
10) Well developed brain.
11) Mammals developed from the therapsid ancestors during the Triassic period.
12) Mammals are heterodontic, meaning that their teeth are different shapes, except those with no teeth at all.
13) Reptiles and fish have teeth that are all basically the same, though they can vary in size throughout the mouth. See image above.
14) The Buccal Cavity (the mouth) has a false palate as a roof, meaning that the nostrils do not lead directly into his mouth.
15) The body is maintained at a constant temperature they generate heat within their bodies metabolically and also have special cooling mechanisms.
16) Highly developed neopallium.
17) Tectum reduced to corpora quadrigemina: functions mainly as a relay center for auditory information and to control visual reflexes.
18) Corpus callosum in eutherians provides additional communication
19) Smell acute except whales and higher apes.
20) Eye typical of amniotes.
21) Tapetum lucidum well developed in nocturnal mammals.
22) Touch- most have vibrissae that are controlled by facial muscles.
23) Lateral movement of jaw during mastication.
24) Viviparous except monotremes which are egg lying.
25) Parental care well developed.