You may know that you are related to apes and monkeys. But did u know that you are also related to bats, tigers, whales, kangaroos, and many more creatures? “Mammals” Presenters: Pema Khandu Phub Lhamo Tshering Lhamo

Describe different classes of mammal with examples Kingdom Animalia ---Phylum Chordata Subphylum Vertebrata Class Mammalia

What is mammals? Mammals are animals that have hair, are warm- blooded, and nourish their young with milk. General characteristics of mammals Warm blooded animals. Skin is more or less covered with hairs except Cetacea. Sudoriporous (sweat) glands and sebaceous (oil) glands are present in the skin. Mammary glands in females to nourish the young ones. External ear (pinnae) are present.

Teeth are heterodont (differentiated into incisors, canines and molars), thecodont (embedded in the alveolar pockets of jaws) and diphyodont (only 2 sets of teeth, milk set replaced by permanent set). Skull with two occipital condyles which are formed entirely by exoccipitals. The lower jaw is composed of a single bone, on each side Vertebrae are gastrocentrous composed of three pieces, the centrum, and two epiphyses.

With few exceptions mammal possess seven cervical vertebrae. The digits in the fore and hind limbs are never more than 5, but often reduced. Presence of muscular diaphragm between thoracic and abdominal cavities. Heart is four chambered with only one left aortic arch. RBC are non-nucleated. Brain with four optic lobes. Kidney is metanephros. Penis is always present. Viviparous (the young develops in the uterus for some time and born alive).

Three classes of Mammals 1.Prototheria (Monotremes): are primitive egg- laying mammals. 2.Metatheria (Marsupials/pouched mammal): their young are born in an extremely immature state. 3.Eutheria (Placental mammals): their young are born at an advanced state.

Prototheria (Egg laying mammal) Primitive mammals Connecting link between the reptile and mammal General characteristics  Skeleton resembles that of reptile  No external pinna present on the ear  Teeth are present only in the young, adults with horny beak  A cloaca is present into which ureters and urinogenitals sinus open  Mammary glands are without nipples  The pectoral girdle possesses large coracoid bones and interclavicle

 The pelvic girdle possesses epipubic bones extending from the pelvis  Vertebrate are without epiphyses  The ribs have only a single head, the tuberculum being absent  In the skull, tympanic bulla and lacrimals are absent ; the jugal is reduced or absent  There is no corpus callosum in the brain  The cochlea is a simple process of the sacculus and not coiled  Testes are abdominal  Females are oviparous  Found in Australia, Tasmania and New Guinea

Examples of prototheria Echidna (spiny ant eater) Ornithorhynchus (Duck-billed platypus)

Metatheria (pouched mammals) General characteristics Young ones are born prematurely after very short gestation Marsupium or rood pouch is present in the females Mammary glands are sebaceous and bearing nipples Epipubic (marsupial) bones are usually present and attached with the pubis Separate coracoid and interclavicle are absent Ribs bear two heads, tuberculum and capitulum

Vertebrae with epiphyses Corpus callosum is feebly developed or absent. Vagina and uterus are double (didelphic condition) Viviparous Placenta is usually absent. Examples Didelphis (Opossum) Dasyurus (Tiger-cat)

Eutheria Placental mammal General characteristics  Give birth to young one  Marsupium (marsupial pouch) is entirely absent.  Mammary glands are well developed with nipples.  Epipubic bones are absent.  Ribs bear two heads, tuberculum and capitulum.  Clooca is absent.  Corpus callosum is present  Urinogenital organs open independently of the rectum.  Testes are usually contained in scortal sacs.

 Warm blooded  External pinna present  Viviparous.  The young always nourished for a considerable time in the uterus by means of allantoicplacenta and born in a relatively advanced state.

Examples Insectivorous mammal- shrew,moles Aerial mammal – bat Aquatic mammal-whales Carnivorous mammal-tiger Hoofed mammal- horse Mammal with proboscis-elephant Primates-apes, monkeys

References Verma, P.S. (1984). A manual of Practical Zoology: Chordates. New Delhi: S. Chand & Company Ltd. Newman, H.H. (1981). The Phylum Chordata. Agra, India : Satish Book Enterprise.

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