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For other uses, see Mammal (disambiguation).
Mammals
Fossil range: Late Triassic – Recent
From Top-left going clockwise: giraffe, golden crown fruit bat, lion, hedgehog
From Top-left going clockwise: giraffe, golden crown fruit bat, lion, hedgehog
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
(unranked) Amniota
Class: Mammalia
Linnaeus, 1758
Subclasses & Infraclasses

Mammals (class Mammalia) are a class of vertebrate animals characterized by the presence of sweat glands, including sweat glands modified for milk production, hair, three middle ear bones used in hearing, and a neocortex region in the brain. The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago Chordates ( Phylum Chordata) are a group of Animals that includes the Vertebrates together with several closely related Invertebrates Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Carl Linnaeus (Latinized as Carolus Linnaeus, also known after his ennoblement as, May 23 new style (13 May old style 1707 who laid the foundations for The Multituberculata (multituberculates are a major branch of mammals that survived for a long period of time but eventually became completely extinct at the end of the In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all Prototheria (ˌproʊtəˈθɪərɪə from Greek prōtos, first + thēr, wild animal is a Taxonomic group or Taxon, to which the order Theria (ˈθɪərɪə from the Greek θηρίον, wild beast is a subclass of Mammals ref> that give birth to live young without Trituberculata is an extinct group of animals existing in the fossil record from about 215 – 85 MYA Metatheria is a grouping within the animal class Mammalia First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes The skin contains two different groups of sweat glands: Apocrine sweat glands and Merocrine sweat glands. Mammary glands are the organs that in Mammals produce Milk for the sustenance of the young Hair is a keratinised protein filament that grows through the epidermis from follicles deep within the Dermis. The middle ear is the portion of the ear internal to the Eardrum, and external to the Oval window of the Cochlea. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce The neocortex ( Latin for "new Bark " or "new Rind " is a part of the Brain of Mammals It is the outer layer of

All mammals other than the monotremes give birth to live young instead of laying eggs. Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead Most mammals also possess specialized teeth, and the largest group of mammals, the placentals, use a placenta during gestation. See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals The placenta is an Ephemeral organ present in placental Vertebrates, such as Eutherial Mammals and Sharks during Gestation The mammalian brain regulates endothermic and circulatory systems, including a four-chambered heart. In Biology, a warm-blooded Animal species is one whose members maintain thermal Homeostasis; that is they keep their body temperature at a roughly constant This is an article about the rock music band "Circulatory System" The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic

Mammals encompass approximately 5,400 species, ranging in size from the Bumblebee Bat (30-40mm) to the Blue Whale (33 m), distributed in about 1,200 genera, 153 families, and 29 orders,[1] though this varies by classification scheme. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. Kitti's Hog-nosed Bat ( Craseonycteris thonglongyai) also known as the bumblebee bat, is an Endangered species of Bat and the only member The Blue Whale ( Balaenoptera musculus) is a Marine mammal belonging to the suborder of Baleen whales (called Mysticeti A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic In Biological classification, family ( Latin This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used

Most mammals belong to the placental group. See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals The four largest orders within the placental mammals are Rodentia (mice, rats, and other small, gnawing mammals), Chiroptera (bats), Carnivora (dogs, cats, bears, and other mammals that primarily eat meat), and Cetartiodactyla (including numerous herbivore species, such as deer, sheep, goats, and buffalos, plus whales). Rodentia is an order of Mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must The diverse order Carnivora (kɑrˈnɪvərə or sometimes /ˌkɑrnɪˈvɔərə/ from Latin carō (stem carn-) "flesh" + vorāre Cetartiodactyla is the Clade to which Whales (including Dolphins and Even-toed ungulates have currently been placed The human species is also a placental mammal, a member of the order Primates. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye

Phylogenetically, Mammalia is defined as all descendants of the most recent common ancestor of monotremes (e. In Genetics, the most recent common ancestor ( MRCA) of any set of Organisms is the most recent individual from which all organisms in the group are directly Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead g. , echidnas and platypuses) and therian mammals (marsupials and placentals). Echidnas (ɨˈkɪdnə also known as spiny anteaters, are four extant Mammal species belonging to the Tachyglossidae family of the The Platypus ( Ornithorhynchus anatinus) is a semi- aquatic Mammal endemic to eastern Australia, including Tasmania. Theria (ˈθɪərɪə from the Greek θηρίον, wild beast is a subclass of Mammals ref> that give birth to live young without Marsupials are an Infraclass of Mammals characterized by a distinctive pouch (called the marsupium) in which females carry their young through See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals This means that some extinct groups of "mammals" are not members of the crown group Mammalia, even though most of them have all the characteristics that traditionally would have classified them as mammals. The Crown Group is a Catering and event caterer in the United Kingdom. These "mammals" are now usually placed in the unranked clade Mammaliaformes. Mammaliaformes ("mammal-shaped" is a Clade that contains the Mammals and their closest extinct relatives

The mammalian line of descent diverged from the sauropsid line at the end of the Carboniferous period. Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 The sauropsids would evolve into modern-day reptiles and birds, while the synapsid branch led to mammals. Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than The first true mammals appeared in the Jurassic period. The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning Modern mammalian orders appeared in the Palaeocene and Eocene epochs of the Palaeogene period. The Paleocene or Palaeocene, "early dawn of the recent" is a geologic epoch that lasted from 65 The Eocene epoch (558 ± 02 - 339 ± 01 Ma) is a major division of the Geologic timescale and the second epoch of the Palaeogene period in The Paleogene (alternatively Palaeogene) is a geologic period and system that began 65

Contents

Distinguishing features

Living mammal species can be identified by the presence of sweat glands, including those that are specialized to produce milk. In its most general form a nipple is a Structure from which a fluid emanates Lactation describes the secretion of Milk from the Mammary glands the process of providing that milk to the young and the period of time that a Mother Milk is an opaque white liquid produced by the Mammary glands of female Mammals (including Monotremes.

However, other features are required when classifying fossils, since soft tissue glands and some other features are not visible in fossils. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Paleontologists use a distinguishing feature that is shared by all living mammals (including monotremes), but is not present in any of the early Triassic synapsids: mammals use two bones for hearing that were used for eating by their ancestors. Palaeontology redirects here For the Scientific journal, see Palaeontology (journal. Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The earliest synapsids had a jaw joint composed of the articular (a small bone at the back of the lower jaw) and the quadrate (a small bone at the back of the upper jaw). The articular bone is in the lower jaw of most Tetrapods, including Amphibians, Sauropsids ("reptiles" Birds and early Synapsids The quadrate bone is part of a skull in most Tetrapods, including Amphibians, Sauropsids ( Reptiles, inclused Birds) and early Most reptiles and non-mammalian synapsids use this system including lizards, crocodilians, dinosaurs (and their descendants the birds), and therapsids (mammal-like "reptiles"). Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage Therapsids are an order of Synapsids (Class Synapsida Traditionally synapsids were referred to as Reptiles and were known as Mammals have a different jaw joint, however, composed only of the dentary (the lower jaw bone which carries the teeth) and the squamosal (another small skull bone). The mandible (from Latin mandibula, "jawbone" or inferior maxillary bone forms the lower Jaw and holds the lower teeth in place The squamosal is a bone of the head of higher Vertebrates It is the principal component of the cheek region in the skull lying below the temporal series and In mammals the quadrate and articular bones have become the incus and malleus bones in the middle ear. For the record label see Incus Records. The incus or anvil is the Anvil -shaped small Bone or ossicle The malleus or hammer is a hammer-shaped small Bone or ossicle of the Middle ear which connects with the Incus and is attached The middle ear is the portion of the ear internal to the Eardrum, and external to the Oval window of the Cochlea. Note: "non-mammalian synapsids" above implies that mammals are a sub-group of synapsids, and that is exactly what cladistics says they are. Cladistics is the hierarchical classification of Species based on evolutionary ancestry

Mammals also have a double occipital condyle: they have two knobs at the base of the skull which fit into the topmost neck vertebra, and other vertebrates have a single occipital condyle. The occipital condyles are undersurface facets of the Occipital bone in vertebrates, which function in articulation with the superior facets of the Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes Paleontologists use only the jaw joint and middle ear as criteria for identifying fossil mammals, as it would be confusing if they found a fossil that had one feature, but not the other.

Anatomy and morphology

Skeletal system

The majority of mammals have seven cervical vertebrae (bones in the neck); this includes bats, giraffes, whales, and humans. In Vertebrates cervical vertebrae (singular vertebra) are those vertebrae immediately behind (posterior to the Skull. The giraffe ( Giraffa camelopardalis) is an African Even-toed ungulate Mammal, the tallest of all land-living Animal Species Whales are marine mammals which are neither Dolphins (ie members of the families Delphinidae or Platanistoidae) nor Porpoises Orcas The few exceptions include the manatee and the two-toed sloth, which have only six cervical vertebrae, and the three-toed sloth with nine cervical vertebrae. Manatees ( family Trichechidae, Genus Trichechus) are large fully aquatic Marine mammals sometimes known as sea "Megalonychidae" redirects here For the Prehistoric members of this family see Ground sloth#Megalonychidae. A vertebra (plural vertebrae) is an individual Irregular bone in the spinal or Vertebral column ( aka ischis a flexuous and flexible column The three-toed sloths are the only members of the Bradypus genus and the Bradypodidae family

Respiratory system

The lungs of mammals have a spongy texture and are honeycombed with epithelium having a much larger surface area in total than the outer surface area of the lung itself. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The lungs of humans are typical of this type of lung. The human lungs are the human organs of respiration. Humans have two Lungs with the left being divided into two lobes and the right into three lobes

Breathing is largely driven by the muscular diaphragm at the bottom of the thorax. For other types of diaphragm see Diaphragm. In the Anatomy of Mammals the thoracic diaphragm is a sheet of Muscle Contraction of the diaphragm pulls the bottom of the cavity in which the lung is enclosed downward. Air enters through the oral and nasal cavities; it flows through the larynx and into the trachea, which branches out into bronchi. Relaxation of the diaphragm has the opposite effect, passively recoiling during normal breathing. During exercise, the diaphragm contracts, forcing the air out more quickly and forcefully. A muscles contraction (also known as a muscle twitch or simply twitch) occurs when a Muscle fibre generates tension through the action of Actin The rib cage itself also is able to expand and contract to some degree, through the action of other respiratory and accessory respiratory muscles. The human rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic (chest cavity and supports the pectoral As a result, air is sucked into or expelled out of the lungs, always moving down its pressure gradient. This type of lung is known as a bellows lung as it resembles a blacksmith's bellows. A bellows is a device for delivering pressurized Air in a controlled quantity to a controlled location

Circulatory system

The mammalian heart has four chambers: the right atrium, right ventricle, left atrium, and left ventricle. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic In Anatomy, the atrium (plural atria) refers to a chamber or space In the Heart, a ventricle is a heart chamber which collects Blood from an atrium (another heart chamber that is smaller than a ventricle and The left atrium is one of the four chambers in the Human Heart. The left ventricle is one of four chambers (two atria and two ventricles in the Human Heart. Atria are for receiving blood; ventricles are for pumping blood to the lungs and body. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive The ventricles are larger than the atria and their walls are thick, because muscular walls are needed to forcefully pump the blood from the heart to the body and lungs. Deoxygenated blood from the body enters the right atrium, which pumps it to the right ventricle. The right ventricle pumps blood to the lungs, where carbon dioxide diffuses out, and oxygen diffuses in. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the From the lungs, oxygenated blood enters the left atrium, where it is pumped to the left ventricle (the largest and strongest of the 4 chambers), which pumps it out to the rest of the body, including the heart's own blood supply.

Nervous system

All mammalian brains possess a neocortex, a brain region that is unique to mammals. The neocortex ( Latin for "new Bark " or "new Rind " is a part of the Brain of Mammals It is the outer layer of

Integumentary system

Mammals have integumentary systems made up of three layers: the outermost epidermis, the dermis, and the hypodermis. The skin is the outer covering of living tissue of an animal (or plant Epidermis is the outermost layer of the Skin. It forms the waterproof protective wrap over the body's surface and is made up of stratified squamous Epithelium with The dermis is a layer of Skin beneath the epidermis that consists of Connective tissue, and cushions the body from stress and strain The hypodermis, also called the hypoderm, subcutaneous tissue, or superficial fascia is the lowermost layer of the Integumentary system in This characteristic is not unique to mammals, since it is found in all vertebrates. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes

The epidermis is typically ten to thirty cells thick; its main function being to provide a waterproof layer. Epidermis is the outermost layer of the Skin. It forms the waterproof protective wrap over the body's surface and is made up of stratified squamous Epithelium with Its outermost cells are constantly lost; its bottommost cells are constantly dividing and pushing upward. The middle layer, the dermis, is fifteen to forty times thicker than the epidermis. The dermis is made up of many components such as bony structures and blood vessels. The hypodermis is made up of adipose tissue. "Adipose" redirects here For the Doctor Who monster see " Partners in Crime " Its job is to store lipids, and to provide cushioning and insulation. The thickness of this layer varies widely from species to species.

Although mammals and other animals have cilia that superficially may resemble it, no other animals except mammals have hair. A cilium (plural cilia) is an Organelle found in eukaryotic cells Cilia are tail-like projections extending approximately Hair is a keratinised protein filament that grows through the epidermis from follicles deep within the Dermis. It is a definitive characteristic of the order. Some mammals have very little, albeit in obscure parts of their bodies, but nonetheless, careful examination reveals the characteristic. None are known to have hair that naturally is blue or green in color although some cetaceans, along with the mandrills appear to have shades of blue skin. The Mandrill ( Mandrillus sphinx) is a Primate of the Cercopithecidae (Old-world Monkeys family closely related to the Baboons Many mammals are indicated as having blue hair or fur, but in all known cases, it has been found to be a shade of gray. The two-toed sloth and the polar bear may seem to have green fur, but this color is caused by algae growths. "Megalonychidae" redirects here For the Prehistoric members of this family see Ground sloth#Megalonychidae. The polar bear ( Ursus maritimus) is a Bear native to the Arctic Ocean and its surrounding seas Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms

Reproductive system

Goat kids will stay with their mother until they are weaned, this is usually about one month
Goat kids will stay with their mother until they are weaned, this is usually about one month

Most mammals give birth to live young (vivipary), but a few, such as the monotremes lay eggs and at least one of them, the platypus, presents a particular sex determination system that in some ways resembles that of birds. A viviparous Animal is an animal employing vivipary: the embryo develops inside the body of the mother as opposed to outside in an egg ( Ovipary Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. The Platypus ( Ornithorhynchus anatinus) is a semi- aquatic Mammal endemic to eastern Australia, including Tasmania. The Platypus ( Ornithorhynchus anatinus) is a semi- aquatic Mammal endemic to eastern Australia, including Tasmania. A sex-determination system is a biological system that determines the development of sexual characteristics in an Organism. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Live birth also occurs in some non-mammalian species, such as guppies, snakes, and hammerhead sharks; thus it is not a distinguishing characteristic of mammals. The guppy (la '''''Poecilia reticulata''''' also known as the millionfish, is one of the most popular freshwater aquarium fish species in the world Hammerhead sharks of the Genus Sphyrna are members of the family Sphyrnidiae.

Mammals have sweat glands, a defining feature present only in mammals. Some of these glands produce milk (in what are called mammary glands), a liquid used by newborns as their primary source of nutrition. Milk is an opaque white liquid produced by the Mammary glands of female Mammals (including Monotremes. Mammary glands are the organs that in Mammals produce Milk for the sustenance of the young The monotremes branched from other mammals early on, and do not have the nipples seen in most mammals, but they do have mammary glands. In its most general form a nipple is a Structure from which a fluid emanates

Physiology

Endothermy

Nearly all mammals are endothermic. Most mammals also have hair to help keep them warm. Like birds, mammals can forage or hunt in cold weather and climes where reptiles and large insects cannot.

Endothermy requires plenty of food energy, so pound for pound mammals eat more food than reptiles. Small insectivorous mammals eat prodigious amounts for their size.

A rare exception, the naked mole rat is ectothermic ("cold-blooded"). The naked mole rat ( Heterocephalus glaber) also known as the sand puppy, or desert mole rat is a burrowing Rodent native to parts Birds are also endothermic, so endothermy is not a defining mammalian feature. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs.

Intelligence

Mammals, such as these humans, are among the most intelligent animals in the world.
Mammals, such as these humans, are among the most intelligent animals in the world.

In intelligent mammals, such as primates, the cerebrum is larger relative to the rest of the brain. A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye The telencephalon (tɛlɛnˈsɛfəlɒn cerebrum, or forebrain is the most Anterior or especially in humans most Dorsal region of the Intelligence itself is not easy to define, but indications of intelligence include the ability to learn, matched with behavioral flexibility. Intelligence (also called intellect) is an Umbrella term used to describe a property of the Mind that encompasses many related abilities such as the capacities Rats, for example, are considered to be highly intelligent as they can learn and perform new tasks, an ability that may be important when they first colonize a fresh habitat. Rats are various medium sized long-tailed Rodents of the superfamily Muroidea A biome is a climatically and geographically defined area of ecologically similar climatic conditions such as communities of Plants Animals and In some mammals, food gathering appears to be related to intelligence: a deer feeding on plants has a brain relatively smaller than a cat that must think to outwit its prey. A deer is a Ruminant Mammal belonging to the family Cervidae. Plants are living Organisms belonging to the kingdom Plantae. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain WikipediaManual of Style (spelling, articles should conform to one overall spelling style of English typically the one most linked to the article topic (if it is geographic [2]

Social structure

The dependence of the young mammal on its mother for nourishment has made possible a period of training. "Mom" "Mum" and "Mommy" redirect here Such training permits the nongenetic transfer of information between generations. The ability of young mammals to learn from the experience of their elders has allowed a behavioral plasticity unknown in any other group of organisms and has been a primary reason for the evolutionary success of mammals. The possibility of training is one of the factors that has made increased brain complexity a selective advantage. Increased associational potential and memory extend the possibility of learning from experience, and the individual can make adaptive behavioral responses to environmental change. In Psychology, memory is an organism's ability to store retain and subsequently retrieve information Individual response to short-term change is far more efficient than genetic response.

Some types of mammals are solitary except for brief periods when the female is in estrus. Others, however, form social groups. Such groups may be reproductive or defensive, or they may serve both functions. In those cases that have been studied in detail, a more or less strict hierarchy of dominance prevails. Within the social group, the hierarchy may be maintained through physical combat between individuals, but in many cases stereotyped patterns of behaviour evolve to displace actual combat, thereby conserving energy while maintaining the social structure.

A pronounced difference between sexes (sexual dimorphism) is frequently extreme in social mammals. In large part this is because dominant males tend to be those that are largest or best-armed. Dominant males also tend to have priority in mating or may even have exclusive responsibility for mating within a “harem. ” Rapid evolution of secondary sexual characteristics, including size, can take place in a species with such a social structure.

A complex behavior termed “play” frequently occurs between siblings, between members of an age class, or between parent and offspring. Play extends the period of maternal training and is especially important in social species, providing an opportunity to learn behaviour appropriate to the maintenance of dominance. [3]

Locomotion

See also Animal locomotion

Mammals evolved from four-legged ancestors. In Biomechanics, animal locomotion is the study of how Animals move. They use their limbs to walk, climb, swim, and fly. Some land mammals have toes that produce claws and hooves for climbing and running. Aquatic mammals such as whales and dolphins have fins which evolved from legs.

Terrestrial

An African Elephant
An African Elephant

See also Terrestrial locomotion

Specialization in habitat preference has been accompanied by locomotor adaptations. African elephants are the species of Elephants in the Genus Loxodonta, one of the two existing genera in Elephantidae. Terrestrial locomotion has Evolved as Animals adapted from aquatic to terrestrial environments Terrestrial mammals have a number of modes of progression. The primitive mammalian stock walked plantigrade—that is, with the digits, bones of the midfoot, and parts of the ankle and wrist in contact with the ground. The limbs of ambulatory mammals are typically mobile, capable of considerable rotation.

Mammals modified for running are termed cursorial. The stance of cursorial species may be digitigrade (the complete digits contacting the ground, as in dogs) or unguligrade (only tips of digits contacting the ground, as in horses). The dog ( Canis lupus familiaris) is a domesticated Subspecies of the gray wolf, a Mammal of the Canidae family of the order The horse ( Equus caballus) is a hoofed ( Ungulate) Mammal, one of eight living species of the family Equidae. In advanced groups limb movement is forward and backward in a single plane.

Saltatory (leaping) locomotion, sometimes called “ricochetal,” has arisen in several unrelated groups (some marsupials, lagomorphs, and several independent lineages of rodents). This mode of locomotion is typically found in mammals living in open habitats. Jumping mammals typically have elongate, plantigrade hind feet, reduced forelimbs, and long tails. Convergent evolution within a given adaptive mode has contributed to the ecological similarity of regional mammalian faunas.

Mammals of several orders have attained great size (elephants, hippopotamuses, and rhinoceroses) and have converged on specializations for a ponderous mode of locomotion referred to as “graviportal. Elephants ( family: Elephantidae) are large land Mammals of the order Proboscidea. The hippopotamus ( Hippopotamus amphibius) from the Greek ἱπποπόταμος ( hippopotamos, ιππος hippos meaning "horse" Rhinoceros (raɪˈnɒsərəs often colloquially abbreviated rhino, is a name used to group five extant species of Odd-toed ungulates in the family ” These animals have no digit reduction and deploy the digits in a circle around the axis of the limb for maximum support, like the pedestal of a column. [3]

Arboreal

See also Scansorial locomotion

Well-adapted arboreal mammals frequently are plantigrade, five-toed, and equipped with highly mobile limbs. There are a diverse range of climbing animals; animals that spend much of their time moving on steep vertical or overhanging surfaces and have appropriate adaptations for such scansorial Some species, including many New World monkeys, have a prehensile tail, which is used like a fifth hand. The New World monkeys are the four families of Primates that are found in Central and South America: Cebidae, Aotidae, Pitheciidae Brachiation, or “arm walking,” in which the animal hangs from branches and moves by a series of long swings, is an adaptation seen in gibbons. Brachiation (from "limb" or "branch" is a form of Arboreal locomotion in which Primates swing from tree limb to tree limb using only their arms Gibbons are the small Apes in the family Hylobatidae. The family is divided into four genera based on their Diploid Chromosome The primitive opposable anthropoid thumb is reduced as a specialization for this method of locomotion. Tarsiers are highly arboreal primates that have expanded pads on the digits to improve grasping, whereas many other arboreal mammals have claws or well-developed nails. Tarsiers are Prosimian Primates of the genus Tarsius, a Monotypic genus in the family Tarsiidae, which is itself the Arboreal is a word meaning "related to or resembling trees" [3]

Sloths travel slowly along branches rather than swinging energetically. The living sloths comprise six Species of medium-sized Mammals that live in Central and South America belonging to the families

Aquatic

Four mammalian groups are fully aquatic. Sirenians (dugongs and manatees) eat plants. Not to be confused with order Sirenidae (aquatic salamanders For the Gothic metal band see Sirenia (band Sirenia Cetaceans (whales, dolphins, and porpoises) and pinnipeds (seals and walruses) eat krill or fish. The Order Cetacea (sɪˈteɪʃiə L cetus, whale includes Whales Dolphins and Porpoises Cetus is Pinnipeds ("fin-feet" lit "winged feet" or fin-footed mammals are a widely distributed and diverse group of semi-aquatic marine Mammals comprising The sea otter eats a variety of invertebrates and fish. The sea otter ( Enhydra lutris) is a Marine mammal native to the coasts of the northern and eastern North Pacific Ocean. An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate Some semiaquatic mammals are very similar to their close land-borne relatives (otters, muskrats, and water shrews, for example). Otters are semi- aquatic (or in one case aquatic) fish-eating Mammals The otter subfamily Lutrinae forms part of the family The muskrat ( Ondatra zibethicus) the only Species in Genus Ondatra, is a medium-sized semi-aquatic Rodent native to North America Other mammals have undergone profound adaptation for swimming and life at sea. Walruses and seals give birth to and nurse their young on land, but cetaceans are completely helpless out of water. The walrus ( Odobenus rosmarus) is a large flippered Marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and The true seals or earless seals are one of the three main groups of Mammals within the seal Suborder, Pinnipedia. They depend on water for mechanical support and thermal insulation. [3] Buoyed by their aquatic environment, whales have evolved into the largest mammals and indeed the largest animals ever.

Aerial

Townsends's Big-eared Bat, Corynorhinus townsendii
Townsends's Big-eared Bat, Corynorhinus townsendii

See also Aerial locomotion

Bats are the only truly flying mammals. A number of Animals have evolved aerial locomotion, either by powered flight or by gliding Only with active flight have the resources of the aerial habitat been successfully exploited. Mammals belonging to other groups (colugos, marsupials, rodents) are adapted for gliding. Marsupials are an Infraclass of Mammals characterized by a distinctive pouch (called the marsupium) in which females carry their young through Rodentia is an order of Mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must A gliding habit is frequently accompanied by scansorial (climbing) locomotion. Many nongliders, such as tree squirrels, are also scansorial. Although the term tree squirrel can refer to any Arboreal member of the family Sciuridae, it is generally in reference to the common and widely distributed [3]

Feeding

To maintain a high constant body temperature is energy expensive- mammals therefore need a nutritious and plentiful diet. While the earliest mammals were probably predators, different species have since adapted to meet their dietary requirements in a variety of ways. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. Some eat animal prey- this is a carnivorous diet (and includes insectivorous diets). A carnivore (ˈkɑrnɪvɔər meaning 'meat eater' ( Latin carne meaning 'flesh' and vorare meaning 'to devour' is any animal with a diet consisting An insectivore is a type of carnivore with a diet that consists chiefly of Insects and similar small creatures Other mammals, called herbivores, eat plants. Herbivory is a form of Predation in which an Organism, known as a herbivore, consumes principally Autotrophs ref name=Campbell>Campbell An herbivorous diet includes sub-types such as fruit-eating and grass-eating. An omnivore eats boths prey and plants. Omnivores (from Latin omne all everything vorare to devour are species that eat both Plants and Animals as their primary Carnivorous mammals have a simple digestive tract, because the proteins, lipids, and minerals found in meat require little in the way of specialized digestion. Digestion is the breaking down of chemicals in the body into a form that can be absorbed Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Plants, on the other hand, contain complex carbohydrates, such as cellulose. Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most Cellulose is an Organic compound with the formula, a Polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4 The digestive tract of a herbivore is therefore host to bacteria that ferment these substances, and make them available for digestion. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have The bacteria are either housed in the multichambered stomach or in a large cecum. In Human anatomy, the stomach is a J-shaped hollow muscular organ of the Gastrointestinal tract involved in the second phase of Digestion, following The cecum or caecum (from the Latin caecus meaning Blind) is a pouch connected to the Ascending colon of the Large The size of an animal is also a factor in determining diet type. Since small mammals have a high ratio of heat losing surface area to heat generating volume, they tend to have high-energy requirements and a high metabolic rate. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Mammals that weigh less than about 18oz (500g) are mostly insectivorous because they cannot tolerate the slow, complex digestive process of a herbivore. Larger animals on the other hand generate more heat and less of this heat is lost. They can therefore tolerate either a slower collection process (those that prey on larger vertebrates) or a slower digestive process (herbivores). Furthermore, mammals that weigh more than 18oz (500g) usually cannot collect enough insects during their waking hours to sustain themselves. Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described The only large insectivorous mammals are those that feed on huge colonies of insects (ants or termites). Ants are social Insects of the family Formicidae and along with the related families of Wasps and Bees belong to the order The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy [2]

Evolutionary history

For more details on this topic, see Evolution of mammals. __FORCETOC__ See also Evolutionary history of life The evolution of mammals from Synapsids (mammal-like " Reptiles quot was a gradual process
Mammaliaformes

Adelobasileus

void

Sinocodon

void

Morganucodonta

void

Docodonta

void

––Hadrocodium


––Mammalia






The evolution of mammals from synapsids, also known as mammal-like "reptiles" was a gradual process which took approximately 70 million years, from the mid-Permian to the mid-Jurassic, and by the mid-Triassic there were many species that looked like mammals. Mammaliaformes ("mammal-shaped" is a Clade that contains the Mammals and their closest extinct relatives Adelobasileus cromptoni is a species of an extinct genus of proto- Mammals from the Late Triassic ( Carnian) about 225 million years ago Sinoconodon rigneyi is an ancient proto- Mammal that appears in the Fossil record in the Late Triassic period about 208 million years ago Docodonta is an order of extinct proto- Mammals that lived during the mid- to late- Mesozoic era Hadrocodium wui is an extinct basal Mammal species that lived during the Lower Jurassic (approx Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than The Permian is a geologic period and system that extends from 299 The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago Note that synapsids are not reptiles at all, but belong to a distinct lineage of tetrapods. Tetrapods ( Greek τετραποδη tetrapoda, Latin Quadruped, "four-footed" are Vertebrate Animals

Evolution

The original synapsid skull structure has one hole behind each eye, in a fairly low position on the skull (lower right in this image).
The original synapsid skull structure has one hole behind each eye, in a fairly low position on the skull (lower right in this image).

The first fully terrestrial vertebrates were amniotes. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes The amniotes are a group of Tetrapod Vertebrates that include the Synapsida ( Mammals and Mammal-like reptiles and Sauropsida Like the amphibians they evolved from, they had legs and lungs. Amniotes' eggs, however, had internal membranes which allowed the developing embryo to breathe but kept water in. An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular This allowed amniotes to lay eggs on dry land, while amphibians generally need to lay their eggs in water.

The first amniotes apparently arose in the late Carboniferous. The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 They descended from amphibians, which were numerous at the time, and lived on land already inhabited by insects, other invertebrates, ferns, mosses, and other plants. Within a few million years two important amniote lineages became distinct: the synapsids, from which mammals are descended; and the sauropsids, from which lizards, snakes, crocodilians, dinosaurs and birds are descended. Synapsids ('fused arch' also known as theropsids ('beast face' are a class of Animals that includes Mammals and everything closer to mammals than Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Lizards are a large and widespread group of Reptiles of the order Squamata, with nearly 5000 species and ranging across all continents except A snake is an elongate Reptile of the suborder Serpentes Like all reptiles snakes are covered in scales. Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. [4] Synapsids have a single hole (temporal fenestra) low on each side of the skull.

One synapsid group, the pelycosaurs, were the most common land vertebrates of the early Permian and included the largest land animals of the time. The pelycosaurs (from Greek πηλυξ pelyx meaning 'bowl' and σαυρος sauros meaning 'lizard' were primitive Late Paleozoic The Permian is a geologic period and system that extends from 299 [5]

Therapsids descended from pelycosaurs in the middle Permian, about 260M years ago, and took over their position as the dominant land vertebrates. Therapsids are an order of Synapsids (Class Synapsida Traditionally synapsids were referred to as Reptiles and were known as The Permian is a geologic period and system that extends from 299 They differ from pelycosaurs in several features of the skull and jaws, including: larger temporal fenestrae; incisors which are equal in size. Incisors (from Latin incidere, "to cut" are the first kind of Tooth in Heterodont Mammals They are located in the Premaxilla [6] The therapsids went through a series of stages, beginning with animals which were very like their pelycosaur ancestors and ending with the Triassic cynodonts, some of which could easily be mistaken for mammals:

The Permian–Triassic extinction event ended the dominance of the therapsids, and in the early Triassic all the medium to large land animal niches were taken over by archosaurs, which were the ancestors of crocodilians, pterosaurs, dinosaurs and birds. The Permian–Triassic (P–Tr extinction event, informally known as the Great Dying, was an Extinction event that occurred, and 70 percent of terrestrial Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. After this "Triassic Takeover" the cynodonts and their descendants could only survive as small, mainly nocturnal insectivores. An insectivore is a type of carnivore with a diet that consists chiefly of Insects and similar small creatures [8] This may actually have accelerated the evolution of mammals - for example the surviving cynodonts and their descendants had to evolve towards warm-bloodedness because their small bodies would otherwise have lost heat quickly, especially as they were active mainly at night.

The first true mammals appeared in the early Jurassic, over 70 million years after the first therapsids and approximately 30 million years after the first mammaliaformes. Hadrocodium appears to be in the middle of the transition to true mammal status — it had a mammalian jaw joint (formed by the dentary and squamosal bones, but there is some debate about whether its middle ear was fully mammalian. Hadrocodium wui is an extinct basal Mammal species that lived during the Lower Jurassic (approx The middle ear is the portion of the ear internal to the Eardrum, and external to the Oval window of the Cochlea. [9]

The earliest known monotreme is Teinolophos, which lived about 123M years ago in Australia. Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead Teinolophos trusleri was a Prehistoric Species of Monotreme, or egg-laying Mammal. For a topic outline on this subject see List of basic Australia topics. Monotremes have some features which may be inherited from the original amniotes:

Unlike other mammals, female monotremes do not have nipples and feed their young by "sweating" milk from patches on their bellies. In its most general form a nipple is a Structure from which a fluid emanates

The oldest known marsupial is Sinodelphys, found in 125M-year old early Cretaceous shale in China's northeastern Liaoning Province. Marsupials are an Infraclass of Mammals characterized by a distinctive pouch (called the marsupium) in which females carry their young through Sinodelphys or "Chinese opossum" is to date the oldest Marsupial Fossil known estimated to be 125 million years old The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by The fossil is nearly complete and includes tufts of fur and imprints of soft tissues. [10]

The living Eutheria ("true beasts") are all placentals. See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals But the earliest known eutherian, Eomaia, found in China and dated to 125M years ago, has some features which are more like those of marsupials (the surviving metatherians):[11]

It is not certain when placental mammals evolved - the earliest undisputed fossils of placentals come from the early Paleocene, after the extinction of the dinosaurs. The Paleocene or Palaeocene, "early dawn of the recent" is a geologic epoch that lasted from 65 [12]

Mammals and near-mammals expanded out of the nocturnal insectivore niche from the mid Juraassic onwards - for example Castorocauda had adaptations for swimming, digging and catching fish. Castorocauda lutrasimilis (also known as the "Jurassic Beaver" is the name given to a small semi-aquatic relative of Mammals living in the middle Jurassic [13]

The traditional view is that: mammals only took over the medium- to large-sized ecological niches in the Cenozoic, after the extinction of the dinosaurs; but then they diversified very quickly, for example the earliest known bat dates from about 50M years ago, only 15M years after the extinction of the dinosaurs. The Cenozoic (also Caenozoic or Cainozoic) Era (ˌsiːnəˈzoʊɪk/ /ˌsɛn- (meaning "new life" ( Greek ( kainos) "new" [14]

On the other hand recent molecular phylogenetic studies suggest that most placental orders diverged about 100M to 85M years ago, but that modern families first appeared in the late Eocene and early Miocene[15] But paleontologists object that no placental fossils have been found from before the end of the Cretaceous[16]

During the Cenozoic several groups of mammals appeared which were much larger than their nearest modern equivalents - but none was even close to the size of the largest dinosaurs with similar feeding habits. This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used In Biological classification, family ( Latin The Eocene epoch (558 ± 02 - 339 ± 01 Ma) is a major division of the Geologic timescale and the second epoch of the Palaeogene period in The Miocene is a geological epoch of the Neogene period and extends from about 23 The Cenozoic (also Caenozoic or Cainozoic) Era (ˌsiːnəˈzoʊɪk/ /ˌsɛn- (meaning "new life" ( Greek ( kainos) "new"

Earliest appearances of features

Hadrocodium, whose fossils date from the early Jurassic, provides the first clear evidence of fully mammalian jaw joints. Hadrocodium wui is an extinct basal Mammal species that lived during the Lower Jurassic (approx The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning

It has been suggested that the original function of lactation (milk production) was to keep eggs moist. Much of the argument is based on monotremes (egg-laying mammals):[17][18][19]

The earliest clear evidence of hair or fur is in fossils of Castorocauda, from 164M years ago in the mid Jurassic. Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead Castorocauda lutrasimilis (also known as the "Jurassic Beaver" is the name given to a small semi-aquatic relative of Mammals living in the middle Jurassic The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning From 1955 onwards some scientists have interpreted the foramina (passages) in the maxillae (upper jaws) and premaxillae (small bones in front of the maxillae) of cynodonts as channels which supplied blood vessels and nerves to vibrissae (whiskers), and suggested that this was evidence of hair or fur. This article is about the Mammal maxilla For Arthropod maxillae see Mouthparts; for Insect maxillae in particular see Insect mouthparts The premaxilla is a pair of small Cranial bones at the very tip of the jaws of many animals usually bearing Teeth, but not always Cynodonts, or 'dog teeth' are a taxon of Therapsids which includes modern mammals and their extinct close relatives [20][21] But foramina do not necessarily show that an animal had vibrissae - for example the modern lizard Tupinambis has foramina which are almost identical to those found in the non-mammalian cynodont Thrinaxodon. Thrinaxodon was a Cynodont, a cat-sized mammal-like "reptile". [22][23]

The evolution of erect limbs in mammals is incomplete — living and fossil monotremes have sprawling limbs. Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead In fact some scientists think that the parasagittal (non-sprawling) limb posture is a synapomorphy (distinguishing characteristic) of the Boreosphenida, a group which contains the Theria and therefore includes the last common ancestor of modern marsupial and placentals - and therefore that all earlier mammals had sprawling limbs. In Evolutionary biology, a synapomorphy is a derived Character state shared by two or more terminal groups ( taxa included in a Cladistic analysis Mammalia is a class of animal within the Phylum Chordata. Mammal classification has been through several iterations since Carolus Linnaeus initially defined Theria (ˈθɪərɪə from the Greek θηρίον, wild beast is a subclass of Mammals ref> that give birth to live young without [24] Sinodelphys (the earliest known marsupial) and Eomaia (the earliest known eutherian) lived about 125M years ago, so erect limbs must have evolved before then. Sinodelphys or "Chinese opossum" is to date the oldest Marsupial Fossil known estimated to be 125 million years old Eomaia scansoria ('climbing dawn mother' is a recently discovered extinct Mammal that may be one of the earliest ancestors of the Eutheria yet to See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals

It is currently very difficult to be confident when endothermy first appeared in the evolution of mammals. In Biology, a warm-blooded Animal species is one whose members maintain thermal Homeostasis; that is they keep their body temperature at a roughly constant Modern monotremes have a lower body temperature and more variable metabolic rate than marsupials and placentals. Monotremes (from the Greek monos 'single' + trema 'hole' referring to the Cloaca) are Mammals that lay eggs ( Prototheria) instead [25] So the main question is when a monotreme-like metabolism evolved in mammals. The evidence found so far suggests Triassic cynodonts may have had fairly high metabolic rates, but is not conclusive. The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago Cynodonts, or 'dog teeth' are a taxon of Therapsids which includes modern mammals and their extinct close relatives In particular it is difficult to see how small animals can maintain a high and stable body temperature without fur, and there is no certain evidence of fur before Castorocauda, about 164M years ago. Castorocauda lutrasimilis (also known as the "Jurassic Beaver" is the name given to a small semi-aquatic relative of Mammals living in the middle Jurassic

Classification

Main article: Mammal classification
Over 70% of mammal species are in the orders Rodentia (blue), Chiroptera (red), and Soricomorpha (yellow)
Over 70% of mammal species are in the orders Rodentia (blue), Chiroptera (red), and Soricomorpha (yellow)

George Gaylord Simpson's "Principles of Classification and a Classification of Mammals" (AMNH Bulletin v. Mammalia is a class of animal within the Phylum Chordata. Mammal classification has been through several iterations since Carolus Linnaeus initially defined Rodentia is an order of Mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must The order Soricomorpha ("shrew-form" is a biological Clade within the class of Mammals In previous years it formed a significant George Gaylord Simpson ( June 16, 1902 &ndash October 6, 1984) was an American Paleontologist. 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 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. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Cladistics is the hierarchical classification of Species based on evolutionary ancestry Though field work gradually made Simpson's classification outdated, it remained the closest thing to an official classification of mammals.

Standardized textbook classification

A somewhat standardized classification system has been adopted by most current mammalogy classroom textbooks. In Zoology, mammalogy is the study of Mammals – a class of Vertebrates with characteristics such as Homeothermic Metabolism The following taxonomy of extant and recently extinct mammals is from Vaughan et al. (2000).

Class Mammalia

McKenna/Bell classification

In 1997, the mammals were comprehensively revised by Malcolm C. McKenna and Susan K. Prototheria (ˌproʊtəˈθɪərɪə from Greek prōtos, first + thēr, wild animal is a Taxonomic group or Taxon, to which the order The Platypus ( Ornithorhynchus anatinus) is a semi- aquatic Mammal endemic to eastern Australia, including Tasmania. Echidnas (ɨˈkɪdnə also known as spiny anteaters, are four extant Mammal species belonging to the Tachyglossidae family of the Theria (ˈθɪərɪə from the Greek θηρίον, wild beast is a subclass of Mammals ref> that give birth to live young without Metatheria is a grouping within the animal class Mammalia First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals Malcolm Carnegie McKenna (1930-2008 was an American Paleontologist. Bell, which has resulted in the "McKenna/Bell classification".

McKenna and Bell, Classification of Mammals: Above the species level, (1997) 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. Palaeontology redirects here For the Scientific journal, see Palaeontology (journal. The American Museum of Natural History ( AMNH) located on the Upper West Side, Manhattan, New York, USA is one of the largest and most New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous 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.

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 nonprofessionals. The legion, in biological Taxonomy, is a non-obligatory Taxonomic rank within the Linnaean hierarchy which is subordinate to the class

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

Extinct groups are represented by a cross (†). In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa.

Class Mammalia

Molecular classification of placentals

Molecular studies based on DNA analysis have suggested new relationships among mammal families over the last few years. Prototheria (ˌproʊtəˈθɪərɪə from Greek prōtos, first + thēr, wild animal is a Taxonomic group or Taxon, to which the order Echidnas (ɨˈkɪdnə also known as spiny anteaters, are four extant Mammal species belonging to the Tachyglossidae family of the The Platypus ( Ornithorhynchus anatinus) is a semi- aquatic Mammal endemic to eastern Australia, including Tasmania. The Multituberculata (multituberculates are a major branch of mammals that survived for a long period of time but eventually became completely extinct at the end of the Triconodonta (also known as Eutriconodonta) is the generic name for a group of early Mammals which were close relatives of the ancestors of all present-day mammals Theria (ˈθɪərɪə from the Greek θηρίον, wild beast is a subclass of Mammals ref> that give birth to live young without Marsupials are an Infraclass of Mammals characterized by a distinctive pouch (called the marsupium) in which females carry their young through Australidelphia is the Superorder that contains roughly three-quarters of all Marsupials including all those native to Australasia and a single For a topic outline on this subject see List of basic Australia topics. The Monito del Monte ("little mountain monkey" Dromiciops gliroides) is a semi-arboreal South American Marsupial which is thought to be more Ameridelphia is the Superorder that includes all Marsupials living in The Americas except for Dromiciops. See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals The superorder Xenarthra is a group of Placental mammals (infraclass Eutheria extant today only in the Americas Epitherians comprise all the Eutherian Mammals except the Xenarthra. The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two families, the Leporidae ( Hares and Rodentia is an order of Mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must Elephant shrews or jumping shrews are small insectivorous Mammals native to Africa, belonging to the Macroscelididae family in the Ferae is a Clade of Mammals consisting of the orders Carnivora (over 260 species across the globe and Pholidota (8 species of pangolin The diverse order Carnivora (kɑrˈnɪvərə or sometimes /ˌkɑrnɪˈvɔərə/ from Latin carō (stem carn-) "flesh" + vorāre The creodonts are an Extinct order of Mammals that lived from the Paleocene to the Miocene epochs The order Insectivora (from Latin insectum "insect" and vorare "to eat" is a now-abandoned biological grouping within the The order Insectivora (from Latin insectum "insect" and vorare "to eat" is a now-abandoned biological grouping within the The Archonta are a group of mammals considered a Superorder in some classifications A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye The treeshrews (or tree shrews) are small Mammals native to the tropical forests of Southeast Asia. Ungulates (meaning roughly "being Hoofed quot or "hoofed animal" are several groups of Mammals most of which use the tips of their toes usually The Aardvark ( Orycteropus afer) ("Digging foot" is a medium-sized burrowing nocturnal Mammal native to Africa. Incertae sedis ( Latin for "of uncertain placement" abbreviated "inc Condylarthra is an order of extinct Placental Mammals known primarily from the Paleocene and Eocene epochs Whales are marine mammals which are neither Dolphins (ie members of the families Delphinidae or Platanistoidae) nor Porpoises Orcas The even-toed ungulates form the Mammal order Artiodactyla. They are Ungulates whose weight is borne (if they have more than two toes about Meridiungulata is a clade with the rank of cohort or super-order possibly part of Laurasiatheria, containing the South-American Ungulates Pyrotheria The odd-toed ungulates are browsing and Grazing Mammals which compose the order Perissodactyla. Elephants ( family: Elephantidae) are large land Mammals of the order Proboscidea. Manatees ( family Trichechidae, Genus Trichechus) are large fully aquatic Marine mammals sometimes known as sea A hyrax (from Greek 'shrewmouse' Afrikaans: klipdassie, from Dutch: klipdas 'rockbadger' is any of four Species of fairly Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Most of these findings have been independently validated by Retrotransposon presence/absence data. Retrotransposons (also called transposons via RNA intermediates are genetic elements that can amplify themselves in a Genome and are ubiquitous components of the Retrotransposon markers are Retrotransposons that are used as cladistic markers The most recent classification systems based on molecular studies have proposed four groups or lineages of placental mammals. See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct 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. The molecular clock (based on the molecular clock hypothesis ( MCH) is a technique in Molecular evolution to relate the divergence time of two Species The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. These molecular findings are consistent with mammal zoogeography:

Following molecular DNA sequence analyses, the first divergence was that of the Afrotheria 110–100 million years ago. Zoogeography is the branch of the science of Biogeography that is concerned with the geographic distribution of Animal Species and their attributes Afrotheria is a Clade of Mammals with the rank of Superorder or Cohort, containing (among others the Golden moles Elephant shrews 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 million years ago. The superorder Xenarthra is a group of Placental mammals (infraclass Eutheria extant today only in the Americas South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a Boreoeutheria (synonymous with Boreotheria) is a Clade that is composed of the sister Taxa Laurasiatheria and Euarchontoglires ( According to an alternative view, the Xenarthra has the Afrotheria as closest allies, forming the Atlantogenata as sistergroup to Boreoeutheria. Atlantogenata is a molecularly-defined Mammal Clade containing the cohorts or super-orders Xenarthra and Afrotheria. The Boreoeutheria split into the Laurasiatheria and Euarchontoglires between 95 and 85 mya; both of these groups evolved on the northern continent of Laurasia. Laurasiatheria is a Clade of rank Cohort or super-order within the Placentalia (living or Eutheria (Placentals and their extinct ancestors The Euarchontoglires (synonymous with Supraprimates) are a Mammalian superorder based on molecular genetic sequence analyses and Retrotransposon presence/absence Laurasia (lɔˈreɪʃiə lɔˈreɪʒə was a Supercontinent that most recently existed as a part of the split of the Pangaean supercontinent in the late Mesozoic 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 Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a The Great American Interchange was an important paleozoogeographic event in which land and freshwater fauna migrated from North America via Central 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. Australasia is a Region of Oceania: New Zealand, Australia, Papua New Guinea, and neighbouring Islands in the Pacific The Old World rats and mice, part of the Subfamily Murinae in the family Muridae, comprise at least 519 species These molecular results are still controversial because they are not reflected by morphological data, and thus not accepted by many systematists. The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism Further there is some indication from Retrotransposon presence/absence data that the traditional Epitheria hypothesis, suggesting Xenarthra as the first divergence, might be true. Epitherians comprise all the Eutherian Mammals except the Xenarthra. The superorder Xenarthra is a group of Placental mammals (infraclass Eutheria extant today only in the Americas

See also

References

  1. ^ (2005-11-16) in Wilson, D. A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye Glires (Latin glīrēs, Dormice) is a Clade consisting of Rodents and lagomorphs ( Rabbits Hares and Pikas The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two families, the Leporidae ( Hares and Rodentia is an order of Mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must Laurasiatheria is a Clade of rank Cohort or super-order within the Placentalia (living or Eutheria (Placentals and their extinct ancestors Erinaceidae is the only living family in the order of the Erinaceomorpha. The order Soricomorpha ("shrew-form" is a biological Clade within the class of Mammals In previous years it formed a significant Ferungulata is traditionally a Clade with the rank of Cohort within the Placental Mammals Established by George Gaylord Simpson in Cetartiodactyla is the Clade to which Whales (including Dolphins and Even-toed ungulates have currently been placed The Order Cetacea (sɪˈteɪʃiə L cetus, whale includes Whales Dolphins and Porpoises Cetus is The even-toed ungulates form the Mammal order Artiodactyla. They are Ungulates whose weight is borne (if they have more than two toes about Pigs, also called hogs or' swine', are Ungulates which have been domesticated as sources of food leather and similar products since ancient times The hippopotamus ( Hippopotamus amphibius) from the Greek ἱπποπόταμος ( hippopotamos, ιππος hippos meaning "horse" Camels are Even-toed ungulates within the Genus Camelus. The Dromedary, one-humped or Arabian camel has a single hump and the The giraffe ( Giraffa camelopardalis) is an African Even-toed ungulate Mammal, the tallest of all land-living Animal Species A deer is a Ruminant Mammal belonging to the family Cervidae. Antelope are Ruminant hoofed Mammals of the family Bovidae in the order of Even-toed ungulates. Cattle, colloquially referred to as cows, are domesticated Ungulates a member of the Subfamily Bovinae of the family The domestic goat ( Capra aegagrus hircus) is a subspecies of goat Domesticated from the Wild goat of Southwest Asia and Eastern Europe Pegasoferae is a recently proposed Superorder of Mammals based on genomic research in Molecular systematics by Nishihara Hasegawa and Okada Zooamata is a proposed Clade of Mammals consisting of Ferae (carnivores and Pangolins and Perissodactyla (odd-toed Ungulates The odd-toed ungulates are browsing and Grazing Mammals which compose the order Perissodactyla. The horse ( Equus caballus) is a hoofed ( Ungulate) Mammal, one of eight living species of the family Equidae. The donkey or ass, Equus asinus, is a member of the Equidae or horse family and an odd-toed ungulate. Zebras are African Equids best known for their distinctive white and black stripes Tapirs (ˈteɪpɚ as in "taper" or /təˈpɪər/ as "ta-pier" are large browsing Mammals, roughly pig-like in shape with short Rhinoceros (raɪˈnɒsərəs often colloquially abbreviated rhino, is a name used to group five extant species of Odd-toed ungulates in the family Ferae is a Clade of Mammals consisting of the orders Carnivora (over 260 species across the globe and Pholidota (8 species of pangolin The diverse order Carnivora (kɑrˈnɪvərə or sometimes /ˌkɑrnɪˈvɔərə/ from Latin carō (stem carn-) "flesh" + vorāre The class Mammalia (the Mammals is divided into two subclasses based on reproductive techniques egg laying mammals (the Monotremes) and mammals which give live birth This is a list of articles dealing with animals that lived and went extinct during prehistoric times The following are the regional Mammals lists by continent Europe North America Alaska Mammalia is a class of animal within the Phylum Chordata. Mammal classification has been through several iterations since Carolus Linnaeus initially defined Although the Mammals are well studied in comparison to other animal groups a number of new species are still being discovered Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Events 534 - A second and final revision of the Codex Justinianus is published E. , and Reeder, D. M. (eds): Mammal Species of the World, 3rd edition, Johns Hopkins University Press. ISBN 0-801-88221-4.  
  2. ^ a b (2001) in Don E. Wilson & David Burnie: Animal: The Definitive Visual Guide to the World's Wildlife, 1st edition, DK Publishing, 86–89. ISBN 978-0789477644.  
  3. ^ a b c d e "mammal. " Encyclopædia Britannica. Standard Edition. Chicago: Encyclopædia Britannica, 2007.
  4. ^ Amniota - Palaeos.
  5. ^ Synapsida overview - Palaeos.
  6. ^ Therapsida - Palaeos.
  7. ^ Kermack (1984). The evolution of mammalian characters. Croom Helm.  
  8. ^ Cynodontia: Overview - Palaeos.
  9. ^ Symmetrodonta - Palaeos.
  10. ^ Oldest Marsupial Fossil Found in China. National Geographic News (December 15, 2003).
  11. ^ Eomaia scansoria: discovery of oldest known placental mammal.
  12. ^ Dinosaur Extinction Spurred Rise of Modern Mammals
  13. ^ Jurassic "Beaver" Found; Rewrites History of Mammals.
  14. ^ Rogue finger gene got bats airborne
  15. ^ Bininda-Emonds, O. R. P. (2007). "The delayed rise of present-day mammals". Nature (446): 507–511.  
  16. ^ Dinosaur Extinction Spurred Rise of Modern Mammals
  17. ^ Oftedal, O. T. (2002). "The mammary gland and its origin during synapsid evolution". Journal of Mammary Gland Biology and Neoplasia 7 (3): 225–252.  
  18. ^ Oftedal, O. T. (2002). "The origin of lactation as a water source for parchment-shelled eggs=Journal of Mammary Gland Biology and Neoplasia" 7 (3): 253–266.  
  19. ^ Lactating on Eggs
  20. ^ Brink, A. S. (1955). "A study on the skeleton of Diademodon". Palaeontologia Africana 3: 3–39.  
  21. ^ Kemp, T. S. (1982). Mammal-like reptiles and the origin of mammals. London: Academic Press, 363.  
  22. ^ Bennett, A. F. and Ruben, J. A. (1986) "The metabolic and thermoregulatory status of therapsids"; pp. 207–218 in N. Hotton III, P. D. MacLean, J. J. Roth and E. C. Roth (eds), "The ecology and biology of mammal-like reptiles", Smithsonian Institution Press, Washington.
  23. ^ Estes, R. (1961). "Cranial anatomy of the cynodont reptile Thrinaxodon liorhinus". Bulletin of the Museum of Comparative Zoology: 165–180.  
  24. ^ Kielan−Jaworowska, Z. (2006). "Limb posture in early mammals: Sprawling or parasagittal". Acta Palaeontologica Polonica 51 (3): 10237–10239.  
  25. ^ Paul, G. S. (1988). Predatory Dinosaurs of the World. New York: Simon and Schuster, 464.  

Bibliography

External links

Dictionary

mammal

-noun

  1. An animal of the class Mammalia, characterized by being warm-blooded, having hair and feeding milk to its young.
  2. (paleontology) A vertebrate with three bones in the inner ear and one in the jaw.
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