Lagomorphs are small-sized mammals with three pairs of continuously growing incisor teeth specialized in gnawing, such as rabbits and hares.Edentatesare mammals with rare or absent teeth, such as sloths, armadillos and anteaters.Cetaceans are aquatic mammals without posterior limbs, such as whales and dolphins.Carnivorous mammals are predators with canine teeth such as dogs, lions and tigers.Perissodactyls or ungulates (hooved), are large animals with an odd number of fingers on each paw, such as horses and rhinos. ![]() Artiodactyls are mammals with an even number of fingers in claws or paws like.The placental animals have been divided into several orders as enumerated below: We note that Marsupials also have a placenta but it is very short lived and does not make any substantial contribution in the nourishment of the foetus. Before birth, the embryo is nourished in mother’s uterus via a specialized organ connected to uterus called placenta. The Placental mammals give birth to live young. There are nearly 4000 described species in Placental mammals, of which most are rodents and bats. A male kangaroo is called a boomer, a female kangaroo a flyer, and a baby kangaroo a joey.Kangaroos are able to withstand dry periods and little rainfall and can survive without water for many months.Further, Kangaroos are able to move more efficiently at high speed in comparison to low speed because of tendons in their hind legs and tail acts as pendulum. Red Kangaroo is largest Marsupial of the world. Most Marsupials are nocturnal and they have best sense of smell and hearing.Gradually, these three continents separated and the marsupials got isolated. They first evolved in South America some 100 million years ago when Australia, South America and Antarctica were joined together.Marsupials have different ecological niches, ranging from moles to insect eaters to plant eaters.This also implies that they have a relatively short gestation Marsupials give birth to a relatively undeveloped young, which often resides in the pouch with the mother for a certain time after birth. Remaining is mostly found in South America and Central America. Most (70%) are found Australia continent which includes Australia, New Zealand, New Guinea and neighbouring islands in the Pacific Ocean. Australia South America and North America (only two species are found north of Mexico). There are around 330 species of Marsupials distributed in three continents viz. Marsupials include kangaroos, wallabies, koala, possums, opossums, wombats, numbat etc. While platypus lays eggs on bank of stream echidnas lay a single egg in a temporary protective pouch on mother’s belly.The young ones get their milk from mammary glands found on mother’s belly.The word “monotreme” means “one opening” which denotes that Monotremes have only one cloaca that is used as anus, unitary tract as well as for reproduction.Monotremes are found only in Australia and New Guinea. Duckbilled Platypus and two species of Echidnas. Currently, only three species of Monotremes are extant viz. Monotremes or Prototherians are egg laying (oviparous) mammals. Monotremes (prototheria), Marsupials (metatheria) and Placentals (Eutheria). ![]() ![]() On this basis, Mammals have been divided into three groups viz. Mostly female mammals give birth to the young ones but there are only a few mammals that lay eggs. Sixthly, the most unique mammalian characteristic is the presence of milk producing glands ( mammary glands) by which the young ones are nourished. Fifthly, all mammals have two pairs of limbs. The hair or fur may differ in proportion. Fourthly, all mammals have some fur or hair on their bodies. ![]() Thirdly, all mammals are endothermic i.e. Secondly, all mammals have lungs and breathe dry air. Firstly, all mammals are vertebrates and have a backbone. Common features of all mammalsĪll mammals have six things in common. In terms of evolution, mammals are most advanced organisms found in almost all habitats in Earth’s biosphere including polar ice caps, deserts, mountains, forests, grasslands and dark caves. Both birds and mammals have evolved from a reptile ancestor.
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