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| Placental mammals
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Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia Xenarthra Dermoptera: Scandentia Primates Rodentia Lagomorpha InsectivoraErinaceidae Soricidae Talpidae Solenodontidae The biological order Insectivora in the past was used as a scrapbasket for a variety of small to very small, relatively unspecialized, insectivorous mammals. The taxonomy has been refined in recent years, and Chiroptera Pholidota CarnivoraCanidae Felidae Herpestidae Hyaenidae Mephitidae Mustelidae Nandiniidae Odobenidae Pinnipedia Procyonidae Ursidae Viverridae The diverse order Carnivora includes over 260 placental mammals. While the Giant Panda is an herbivore, nearly all others eat meat Perissodactyla Artiodactyla CetaceaMysticeti Odontoceti see text The order Cetacea includes whales, dolphins and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal," was more general, It comes from Greek ketos (" sea monster")
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The majority of living mammals are placental: the other two extant groups are the Monotremata and the Marsupialia; there are other groups of extinct mammals. The Placentalia are distinguished from other mammals in that the foetus is nourished during gestation via a placenta while, in general, this is not the case with other mammals. ( Bandicoots are a conspicuous exception to this rule.) Placental mammals are viviparous.
Eutheria is a taxon introduced by Thomas Henry Huxley in 1880, containing the placental mammals and the nearest ancestors of placental mammals (which are known only from the fossil record). The name itself means 'true beasts'. The closest living relatives of the eutheres are part of the subclass Marsupialia.
The earliest known Placentalia species is Eomaia from the Lower Cretaceous of China. It is undoubtably a member of Placentalia, but the hips of the animal are too narrowly built to have allowed the birth of well-developed young. This strongly suggests that a placenta played little rôle in the development of young.
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