Mammal

The mammals are the class of vertebrate animals characterized by the presence of mammary glands, which in females produce milk for the nourishment of young; the presence of hair or fur; and which have endothermic or "warm-blooded" bodies. The brain regulates endothermic and circulatory systems, including a four-chambered heart. Mammals encompass some 5500 species, distributed in about 1200 genera, 152 families and up to 46 orders, though this varies depending on the classification scheme adopted.

Classification

Main article: Mammal classification

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George Gaylord Simpson's classic "Principles of Classification and a Classification of Mammals" (AMNH Bulletin v. 85, 1945) was the original source for the taxonomy listed here. Simpson laid out a systematics of mammal origins and relationships that was universally taught until the end of the 20th century. Since Simpson's 1945 classification, the paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics. Though field work gradually made Simpson's classification outdated, it remained the closest thing to an official classification of mammals.

Related Topics:
George Gaylord Simpson - 20th century - Paleontological record - Cladistics

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Standardized textbook classification

A somewhat standardized classification system has been adopted by most current mammalogy classroom textbooks. The following taxonomy of extant and recently extinct mammals is taken from Vaughan et al. (2000).

Related Topics:
Mammalogy - Vaughan et al. (2000)

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Class Mammalia

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• Subclass Prototheria - monotremes: platypus and echidnas
• Subclass Theria - live-bearing mammals
• Infraclass Metatheria - marsupials
• Infraclass Eutheria - placentals

McKenna/Bell classification

In 1997, the mammals were comprehensively revised by Malcolm C. McKenna and Susan K. Bell, which has resulted in the "McKenna/Bell classification".

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is the most comprehensive work to date on the systematics, relationships, and occurrences of all mammal taxa, living and extinct, down through the rank of genus. The new McKenna/Bell classification was quickly accepted by paleontologists. The authors work together as paleontologists at the American Museum of Natural History, New York. McKenna inherited the project from Simpson and, with Bell, constructed a completely updated hierarchical system, covering living and extinct taxa that reflects the historical genealogy of Mammalia.

Related Topics:
Paleontologists - American Museum of Natural History

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The McKenna/Bell hierarchical listing of all of the terms used for mammal groups above the species includes extinct mammals as well as modern groups, and introduces some fine distinctions such as legions and sublegions (ranks which fall between classes and orders) that are likely to be glossed over by the layman.

Related Topics:
Legions - Sublegions

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The published re-classification forms both a comprehensive and authoritative record of approved names and classifications and a list of invalid names.

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Click on the highlighted link for a table comparing the traditional and the new McKenna/Bell classifications of mammals

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Extinct groups are represented by †.

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Class Mammalia

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• Subclass Prototheria: monotremes: platypuses and echidnas
• Subclass Theriiformes: live-bearing mammals and their prehistoric relatives
• Infraclass †Allotheria: multituberculates
• Infraclass †Triconodonta: triconodonts
• Infraclass Holotheria: modern live-bearing mammals and their prehistoric relatives
• Supercohort Theria: live-bearing mammals
• Cohort Marsupialia: marsupials
• Magnorder Australidelphia: Australian marsupials and the monito-del-monte
• Magnorder Ameridelphia: New World marsupials
• Cohort Placentalia: placentals
• Magnorder Xenarthra: xenarthrans
• Magnorder Epitheria: epitheres
• Grandorder Anagalida: lagomorphs, rodents, and elephant shrews
• Grandorder Ferae: carnivorans, pangolins, creodonts, and relatives
• Grandorder Lipotyphla: insectivorans
• Grandorder Archonta: bats, primates, colugos, and tree shrews
• Grandorder Ungulata: ungulates
• Order Tubulidentata incertae sedis: aardvark
• Mirorder Eparctocyona: condylarths, whales, and artiodactyls
• Mirorder †Meridiungulata: South American ungulates
• Mirorder Altungulata: perissodactyls, elephants, manatees, and hyraxes

Molecular classification of mammals

Molecular studies based on DNA analysis have suggested new relationships among mammal families over the last few years. The most recent classification systems based on molecular studies have proposed four groups or lineages of placental mammals. Molecular clocks suggest that these clades diverged from early common ancestors in the Cretaceous, but fossils have not been found to corroborate this hypothesis. These molecular findings are consistent with mammal zoogeography:

Related Topics:
Molecular clock - Zoogeography

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The first divergence was that of the Afrotheria 110–100 mya. The Afrotheria proceeded to evolve and diversify in the isolation of the African-Arabian continent. The Xenarthra, isolated in South America, diverged from the Boreoeutheria approximately 100–95 mya. The Boreoeutheria split into the Laurasiatheria and Euarchontoglires between 95 and 85 mya; both of these groups evolved on the northern continent of Laurasia. After tens of millions of years of relative isolation, Africa-Arabia collided with Eurasia, exchanging Afrotheria and Boreoeutheria. The formation of the Isthmus of Panama linked South America and North America, which facilitated the exchange of mammal species in the Great American Interchange. The traditional view that no placental mammals reached Australasia until about 5 million years ago when bats and murine rodents arrived has been challenged by recent evidence and may need to be reassessed. It should however be noted that these molecular results are still controversial because they are not reflected by morphological data and thus not accepted by many systematists.

Related Topics:
Afrotheria - Xenarthra - South America - Boreoeutheria - Laurasiatheria - Euarchontoglires - Laurasia - Isthmus of Panama - North America - Great American Interchange - Australasia - Murine - Morphological

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• Group I: Afrotheria
• Order Macroscelidea: elephant shrews (Africa).
• Order Afrosoricida
• Order Tubulidentata: aardvark (Africa south of the Sahara).
• Clade Paenungulata
• Order Hyracoidea: hyraxes, dassies (Africa, Arabia).
• Order Proboscidea: elephants (Africa, Southeast Asia).
• Order Sirenia
• Group II: Xenarthra
• Order Xenarthra: sloths and anteaters (Neotropical) and armadillos (Neotropical and Nearctic)
• Clade Boreoeutheria
• Group III Euarchontoglires
• Superorder Euarchonta
• Order Scandentia: tree shrews (Southeast Asia).
• Order Dermoptera: flying lemurs or colugos (Southeast Asia).
• Order Primates: lemurs, bushbabies, monkeys, apes (cosmopolitan).
• Superorder Glires
• Order Lagomorpha: pikas, rabbits, hares (Eurasia, Africa, Americas).
• Order Rodentia: rodents (cosmopolitan)
• Group IV: Laurasiatheria
• Order Insectivora: eulipotyphlan insectivorans
• Order Chiroptera: bats (cosmopolitan)
• Order Cetartiodactyla: cosmopolitan; includes former orders Cetacea (whales, dolphins and porpoises) and Artiodactyla (even-toed ungulates, including pigs, hippopotamus, camels, giraffe, deer, antelope, cattle, sheep, goats).
• Clade Zooamata
• Order Perissodactyla: odd-toed ungulates
• Clade Ferae
• Order Pholidota: pangolins, scaly anteaters (Africa, South Asia).
• Order Carnivora: carnivorans (cosmopolitan)

Classification system used in related articles

In light of all the options available, the following classification system has been adopted for use in related articles.

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Class Mammalia

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• Subclass/Order Monotremata: egg-laying mammals
• Order Monotremata: echidnas and platypus
• Subclass Marsupialia: marsupials
• Order Didelphimorphia: New World opossums
• Order Paucituberculata: shrew opossums
• Order Microbiotheria: Monito del Monte
• Order Dasyuromorphia: marsupial carnivores
• Order Notoryctemorphia: marsupial mole
• Superorder Syndactyla: syndactylous marsupials
• Order Peramelemorphia: bandicoots and bilbies
• Order Diprotodontia: koalas, wombats, kangaroos, possums, etc.
• Subclass Placentalia
• Order Xenarthra: sloths, anteaters, armadillos
• Order Pholidota: pangolins
• Superorder Glires
• Order Rodentia: rodents
• Order Lagomorpha: rabbits, hares, and pikas
• Order Macroscelidea: elephant shrews
• Superorder Archonta:
• Order Primates: primates
• Order Scandentia: tree shrews
• Order Chiroptera: bats
• Order Dermoptera: colugos
• Order Insectivora: shrews, tenrecs, moles, hedgehogs, etc.
• Order Carnivora: dogs, cats, weasels, seals, etc.
• Superorder Ungulata: ungulates
• Order Tubulidentata: aardvark
• Order Hyracoidea: hyraxes
• Order Proboscidea: elephants
• Order Sirenia: manatees, dugong
• Order Perissodactyla: horses, tapirs, rhinoceroses
• Order Artiodactyla: even-toed ungulates
• Order Cetacea: whales