<P> Most mammals , including the six most species - rich orders , belong to the placental group . The three largest orders in numbers of species are Rodentia : mice , rats , porcupines , beavers , capybaras and other gnawing mammals ; Chiroptera : bats ; and Soricomorpha : shrews , moles and solenodons . The next three biggest orders , depending on the biological classification scheme used , are the Primates including the apes , monkeys and lemurs ; the Cetartiodactyla including whales and even - toed ungulates ; and the Carnivora which includes cats , dogs , weasels , bears , seals and allies . According to Mammal Species of the World , 5,416 species were identified in 2006 . These were grouped into 1,229 genera , 153 families and 29 orders . In 2008 , the International Union for Conservation of Nature ( IUCN ) completed a five - year Global Mammal Assessment for its IUCN Red List , which counted 5,488 species . According to a research published in the Journal of Mammalogy in 2018 , the number of recognized mammal species is 6,495 species included 96 recently extinct . </P>
<P> Most mammals , including the six most species - rich orders , belong to the placental group . The three largest orders in numbers of species are Rodentia : mice , rats , porcupines , beavers , capybaras and other gnawing mammals ; Chiroptera : bats ; and Soricomorpha : shrews , moles and solenodons . The next three biggest orders , depending on the biological classification scheme used , are the Primates including the apes , monkeys and lemurs ; the Cetartiodactyla including whales and even - toed ungulates ; and the Carnivora which includes cats , dogs , weasels , bears , seals and allies . According to Mammal Species of the World , 5,416 species were identified in 2006 . These were grouped into 1,229 genera , 153 families and 29 orders . In 2008 , the International Union for Conservation of Nature ( IUCN ) completed a five - year Global Mammal Assessment for its IUCN Red List , which counted 5,488 species . According to a research published in the Journal of Mammalogy in 2018 , the number of recognized mammal species is 6,495 species included 96 recently extinct . </P>
the number of orders in class mammalia is
the number of orders in class mammalia is
29
29