Giant hutia
The giant hutias are an extinct group of large rodents known from fossil and subfossil material in the West Indies. One species, "Amblyrhiza inundata", is estimated to have weighed between , big specimens being as large as an American black bear. This is twice as large as the capybara, the largest rodent living today, but still much smaller than "Josephoartigasia monesi", the largest rodent known. These animals were probably used as a food source by aboriginal humans. All giant hutias are in a single family, Heptaxodontidae, which contains no living species; this grouping seems to be paraphyletic and artificial, however.
Mammal
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.