The Proboscidea are a taxonomic order of afrotherian mammals containing one living family and several extinct families. This order, first described by J. Illiger in 1811, encompasses the trunked mammals. In addition to their enormous size proboscideans are distinguished by tusks and long, muscular trunks. Beginning in the mid-Miocene, most members of this order were large animals; the largest land mammal today is the African elephant weighing up to 10.4 tonnes with a shoulder height of up to 4 m. The largest land mammal of all time may have been a proboscidean: Palaeoloxodon namadicus, which may have weighed up to 22 t with a shoulder height up to 5.2 m, surpassing several sauropod dinosaurs. The earliest known proboscidean is Eritherium, followed by Phosphatherium, a small animal about the size of a fox; these both date from late Paleocene deposits of Morocco. Proboscideans evolved in Africa, where they increased in size and diversity during the Eocene and early Oligocene. Several primitive families from these epochs have been described, including the Numidotheriidae and Barytheriidae, all found in Africa.
When Africa became connected to Europe and Asia after the shrinking of the Tethys Sea, proboscideans began to migrate into Eurasia, some families reached North America. Proboscideans found in Eurasia in addition to Africa include the Deinotheriidae, which thrived during the Miocene and into the early Quaternary, Stegolophodon, an early genus of the disputed family Stegodontidae. Most families of the Proboscidea are now extinct, including all proboscideans that lived in the Americas and northern Asia. Many of these extinctions occurred during or shortly after the last glacial period. Extinct species include the last examples of gomphotheres in the Americas, the American mastodon of family Mammutidae in North America, numerous stegodonts once found in Asia, the last of the mammoths throughout the Northern Hemisphere, several species of dwarf elephants found on various islands scattered around the world. Below is the current taxonomy of the proboscidean genera as of 2017. Proboscidea Illiger, 1811 †Eritherium Gheerbrant, 2009 †Moeritherium Andrews, 1901 †Plesielephantiformes Shoshani et al. 2001 †Numidotheriidae Shoshani & Tassy, 1992 †Phosphatherium Gheerbrant et al. 1996 †Arcanotherium Delmer, 2009 †Daouitherium Gheerbrant & Sudre, 2002 †Numidotherium Mahboubi et al. 1986 †Barytheriidae Andrews, 1906 †Omanitherium Seiffert et al. 2012 †Barytherium Andrews, 1901 †Deinotheriidae Bonaparte, 1841 †Chilgatherium Sanders et al. 2004 †Prodeinotherium Ehik, 1930 †Deinotherium Kaup, 1829 Elephantiformes Tassy, 1988 †Eritreum Shoshani et al. 2006 †Hemimastodon Pilgrim, 1912 †Palaeomastodon Andrews, 1901 †Phiomia Andrews & Beadnell, 1902 Elephantimorpha Tassy & Shoshani, 1997 †Mammutidae Hay, 1922 †Losodokodon Rasmussen & Gutierrez, 2009 †Eozygodon Tassy & Pickford, 1983 †Zygolophodon Vacek, 1877 †Sinomammut Mothé et al. 2016 †Mammut Blumenbach, 1799 Elephantida Tassy & Shoshani, 1997 †Choerolophodontidae Gaziry, 1976 †Afrochoerodon Pickford, 2001 †Choerolophodon Schlesinger, 1917 †Amebelodontidae Barbour, 1927 †Afromastodon Pickford, 2003 †Progomphotherium Pickford, 2003 †Eurybelodon Lambert, 2016 †Serbelodon Frick, 1933 †Archaeobelodon Tassy, 1984 †Protanancus Arambourg, 1945 †Amebelodon Barbour, 1927 †Konobelodon Lambert, 1990 †Torynobelodon Barbour, 1929 †Aphanobelodon Wang et al. 2016 †Platybelodon Borissiak, 1928 †Gomphotheriidae Hay, 1922 †Gomphotherium Burmeister, 1837 †Gnathabelodon Barbour & Sternberg, 1935 †Eubelodon Barbour, 1914 †Stegomastodon Pohlig, 1912 †Sinomastodon Tobien et al. 1986 †Notiomastodon Cabrera, 1929 †Rhynchotherium Falconer, 1868 †Cuvieronius Osborn, 1923 Elephantoidea Gray, 1821 †Anancidae Hay, 1922 †Anancus Aymard, 1855 †Morrillia Osborn, 1924 †Paratetralophodon Tassy, 1983 †Pediolophodon Lambert, 2007 †Tetralophodon Falconer, 1857 †Stegodontidae Osborn, 1918 †Stegolophodon Schlesinger, 1917 †Stegodon Falconer, 1857 Elephantidae Gray, 1821 †Stegotetrabelodontinae Aguirre, 1969 †Stegodibelodon Coppens, 1972 †Stegotetrabelodon Petrocchi, 1941 †Selenotherium Mackaye, Brunet & Tassy, 2005 Elephantinae Gray, 1821 †Primelephas Maglio, 1970 Loxodonta Anonymous, 1827 †Palaeoloxodon Matsumoto, 1924 †Mammuthus Brookes, 1828 Elephas Linnaeus, 1758 Ronald M. Nowak, Walker's Mammals of the World, Baltimore: Johns Hopkins University Press, ISBN 978-0-8018-5789-8, LCCN 98023686
Henry Fairfield Osborn
Henry Fairfield Osborn, Sr. was an American paleontologist and geologist. He was the president of the American Museum of Natural History for 25 years. Son of the prominent railroad tycoon William Henry Osborn and his wife, Virginia Reed Osborn, Henry Fairfield Osborn was born in Fairfield, Connecticut, 1857, he studied at Princeton University, obtaining a B. A. in geology and archaeology, where he was mentored by paleontologist Edward Drinker Cope. Two years Osborn took a special course of study in anatomy in the College of Physicians and Surgeons and Bellevue Medical School of New York under Dr. William H. Welch, subsequently studied embryology and comparative anatomy under Thomas Huxley as well as Francis Maitland Balfour at Cambridge University, England. In 1880, Osborn obtained a Sc. D. in paleontology from Princeton, becoming a lecturer in Biology and Professor of Comparative Anatomy from the same university. In 1891, Osborn was hired by Columbia University as a professor of zoology; as a curator, he assembled a remarkable team of fossil hunters and preparators, including William King Gregory.
On November 23, 1897 he was elected member of the Boone and Crockett Club, a wildlife conservation organization founded by Theodore Roosevelt and George Bird Grinnell. Thanks to his considerable family wealth and personal connections, he succeeded Morris K. Jesup as the president of the museum's Board of Trustees in 1908, serving until 1933, during which time he accumulated one of the finest fossil collections in the world. Additionally, Osborn served as President of the New York Zoological Society from 1909 to 1925. Long a member of the US Geological Survey, Osborn became its senior vertebrate paleontologist in 1924, he led many fossil-hunting expeditions into the American Southwest, starting with his first to Colorado and Wyoming in 1877. Osborn conducted research on Tyrannosaurus brains by cutting open fossilized braincases with a diamond saw, he accumulated a number of prizes for his work in paleontology. In 1901, Osborn was elected a Fellow of the American Academy of Sciences, he described and named Ornitholestes in 1903, Tyrannosaurus rex in 1905, Pentaceratops in 1923, Velociraptor in 1924.
In 1929 Osborn was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences. Despite his considerable scientific stature during the 1900s and 1910s, Osborn's scientific achievements have not held up well, for they were undermined by ongoing efforts to bend scientific findings to fit his own racist and eugenist viewpoints, his legacy at the American Museum has proved more enduring. Biographer Ronald Rainger has described Osborn as "a first-rate science administrator and a third-rate scientist." Indeed, Osborn's greatest contributions to science lay in his efforts to popularize it through visual means. At his urging, staff members at the American Museum of Natural History invested new energy in display, the museum became one of the pre-eminent sites for exhibition in the early twentieth century as a result; the murals, habitat dioramas, dinosaur mounts executed during his tenure at the museum attracted millions of visitors, inspired other museums to imitate his innovations.
But his decision to invest in exhibition alienated certain members of the scientific community and angered curators hoping to spend more time on their own research. Additionally, his efforts to imbue the museum's exhibits and educational programs with his own racist and eugenist beliefs disturbed many of his contemporaries and have marred his legacy. An African dwarf crocodile, Osteolaemus osborni, was named in his honor by Karl Patterson Schmidt in 1919. Osborn developed his own evolution theory of man's origins called the "Dawn Man Theory", his theory was founded on the discovery of Piltdown Man, dated to the Late Pliocene. Writing before Piltdown was exposed as a hoax, the Eoanthropus or "Dawn Man" Osborn maintained sprang from a common ancestor with the ape during the Oligocene period which he believed developed separately during the Miocene. Therefore, Osborn argued that all apes following the pre-Darwinian classification of Linnaeus had evolved parallel to the ancestors of man. Osborn himself wrote: We have all borne with the ape and monkey and ape hypothesis long enough are we are glad to welcome this new idea of the aristocracy of man back to a remote period than the beginning of the stone age.
While believing in common ancestry between man and ape, Osborn denied that this ancestor was ape-like. The common ancestor between man and ape Osborn always maintained was more Human than ape. Writing to Arthur Keith in 1927, he remarked "when our Oligocene ancestor is found it will not be an ape, but it will be pro-human", his student William K. Gregory called Osborn's idiosyncratic view on man's origins as a form of "Parallel Evolution" but many creationists misinterpreted Osborn frustrating him, believed he was asserting man had never evolved from a lower life form. Osborn was a supporter of Edward Drinker Cope's neo-Lamarckism, however, he abandoned this view. Osborn became a proponent of organic selection
Binomial nomenclature called binominal nomenclature or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomen, binominal name or a scientific name; the first part of the name – the generic name – identifies the genus to which the species belongs, while the second part – the specific name or specific epithet – identifies the species within the genus. For example, humans belong within this genus to the species Homo sapiens. Tyrannosaurus rex is the most known binomial; the formal introduction of this system of naming species is credited to Carl Linnaeus beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus; the application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature for animals and the International Code of Nomenclature for algae and plants.
Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules. In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not when derived from a proper noun such as the name of a person or place. Both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a binomial name is given, at least when it is first mentioned, the date of publication may be specified. In zoology "Patella vulgata Linnaeus, 1758"; the name "Linnaeus" tells the reader who it was that first published a description and name for this species of limpet. "Passer domesticus". The original name given by Linnaeus was Fringilla domestica; the ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs include such information.
In botany "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus". "Hyacinthoides italica Rothm. – Linnaeus first named this bluebell species Scilla italica. The name is composed of two word-forming elements: "bi", a Latin prefix for two, "-nomial", relating to a term or terms; the word "binomium" was used in Medieval Latin to mean a two-term expression in mathematics. Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name, from one to several words long. Together they formed a system of polynomial nomenclature; these names had two separate functions. First, to designate or label the species, second, to be a diagnosis or description. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; such "polynomial names" may sometimes look like binomials, but are different. For example, Gerard's herbal describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort.
The other... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels; the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more known by his Latinized name Carl Linnaeus, it was in his 1753 Species Plantarum that he first began using a one-word "trivial name" together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as specific name; the Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word. Linnaeus's trivial names introduced an important new idea, namely that the function of a name could be to give a species a unique label; this meant. Thus Gerard's Phalangium ephemerum virginianum became Tradescantia virgi
The Elephantidae are a family of large, herbivorous mammals collectively called elephants and mammoths. These are terrestrial large mammals with a snout modified into a trunk and teeth modified into tusks. Most genera and species in the family are extinct. Only two genera and Elephas, are living; the family was first described by John Edward Gray in 1821, assigned to taxonomic ranks within the order Proboscidea. The Elephantidae have been revised by various authors to include or exclude other extinct proboscidean genera. Scientific classification of Elephantidae taxa embraces an extensive record of fossil specimens, over millions of years, some of which existed until the end of the last ice age; some species were extirpated more recently. The discovery of new specimens and proposed cladistics have resulted in systematic revisions of the family and related proboscideans. Elephantids are classified informally as the elephant family, or in a paleobiological context as elephants and mammoths; the common name elephant refers to the living taxa, the modern elephants, but may refer to a variety of extinct species, both within this family and in others.
Other members of the Elephantidae members of Mammuthus, are referred to by the common name mammoth. The family diverged from a common ancestor of the mastodons of Mammutidae; the classification of proboscideans is unstable and has been revised. The following cladogram shows the placement of the genus Mammuthus among other proboscideans, based on hyoid characteristics: The systematics of the living subspecies and species, the modern elephants, has undergone several revisions. A list of the extant Elephantidae includes: Elephantidae Loxodonta L. africana African bush elephant L. a. pharaoensis North African elephant† L. cyclotis African forest elephant Elephas E. maximus Asian elephant E. m. maximus Sri Lankan elephant E. m. indicus Indian elephant E. m. sumatranus Sumatran elephant E. m. borneensis Borneo elephant E. m. sondaicus Javan elephant† E. m. asurus Syrian elephant† Although the fossil evidence is uncertain, by comparing genes, scientists have discovered evidence that elephantids and other proboscideans share a distant ancestry with Sirenia and Hyracoidea.
These have been assigned with the demostylians to the clade Proboscidea. In the distant past, members of the various hyrax families grew to large sizes, the common ancestor of all three modern families is thought to have been some kind of amphibious hyracoid. One hypothesis is that these animals spent most of their time under water, using their trunks like snorkels for breathing. Modern elephants have this ability and are known to swim in that manner for up to six hours and 50 km. In the past, a much wider variety of genera and species was found, including the mammoths and stegodons. Media related to Elephantidae at Wikimedia Commons Data related to Elephantidae at Wikispecies
The Pliocene Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the youngest epoch of the Neogene Period in the Cenozoic Era; the Pliocene is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations within the Pleistocene, the Pliocene included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, is now included in the Pleistocene. As with other older geologic periods, the geological strata that define the start and end are well identified but the exact dates of the start and end of the epoch are uncertain; the boundaries defining the Pliocene are not set at an identified worldwide event but rather at regional boundaries between the warmer Miocene and the cooler Pliocene. The upper boundary was set at the start of the Pleistocene glaciations. Charles Lyell gave the Pliocene its name in Principles of Geology; the word pliocene comes from the Greek words πλεῖον and καινός and means "continuation of the recent", referring to the modern marine mollusc fauna.
H. W. Fowler called the term Pliocene a "regrettable barbarism" and an indication that "a good classical scholar" such as Lyell should have requested a philologist's help when coining words. To summarize the usage of these "regrettable barbarisms" in the labelling of the Cenozoic era: with the understanding that these are all new relative to the Mesozoic and Paleozoic eras. In the official timescale of the ICS, the Pliocene is subdivided into two stages. From youngest to oldest they are: Piacenzian Zanclean The Piacenzian is sometimes referred to as the Late Pliocene, whereas the Zanclean is referred to as the Early Pliocene. In the system of North American Land Mammal Ages include Hemphillian, Blancan; the Blancan extends forward into the Pleistocene. South American Land Mammal Ages include Montehermosan and Uquian. In the Paratethys area the Pliocene contains the Romanian stages; as usual in stratigraphy, there are many other local subdivisions in use. In Britain the Pliocene is divided into the following stages: Gedgravian, Pre-Ludhamian, Thurnian, Bramertonian or Antian, Pre-Pastonian or Baventian and Beestonian.
In the Netherlands the Pliocene is divided into these stages: Brunssumian C, Reuverian A, Reuverian B, Reuverian C, Tiglian A, Tiglian B, Tiglian C1-4b, Tiglian C4c, Tiglian C5, Tiglian C6 and Eburonian. The exact correlations between these local stages and the ICS stages is still a matter of detail; the global average temperature in the mid-Pliocene was 2–3 °C higher than today, carbon dioxide levels were the same as today, global sea level was 25 m higher. The northern hemisphere ice sheet was ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma; the formation of an Arctic ice cap is signaled by an abrupt shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic and North Pacific ocean beds. Mid-latitude glaciation was underway before the end of the epoch; the global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas. Continents continued to drift, moving from positions as far as 250 km from their present locations to positions only 70 km from their current locations.
South America became linked to North America through the Isthmus of Panama during the Pliocene, making possible the Great American Interchange and bringing a nearly complete end to South America's distinctive large marsupial predator and native ungulate faunas. The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean. Africa's collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean; the border between the Miocene and the Pliocene is the time of the Messinian salinity crisis. Sea level changes exposed the land bridge between Asia. Pliocene marine rocks are well exposed in the Mediterranean and China. Elsewhere, they are exposed near shores. During the Pliocene parts of southern Norway and southern Sweden, near sea level rose. In Norway this rise elevated the Hardangervidda plateau to 1200 m in the Early Pliocene.
In Southern Sweden similar movements elevated the South Swedish highlands leading to a deflection of the ancient Eridanos river from its original path across south-central Sweden into a course south of Sweden. The change to a cooler, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, grasslands spread on all continents. Tropical forests were limited to a tight band around the equator, in addition to dry savannahs, deserts appeared in Asia and Africa. Both marine and co
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
Mammals are vertebrate animals constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding their young, a neocortex, fur or hair, three middle ear bones. These characteristics distinguish them from reptiles and birds, from which they diverged in the late Triassic, 201–227 million years ago. There are around 5,450 species of mammals; the largest orders are the rodents and Soricomorpha. The next three are the Primates, the Cetartiodactyla, the Carnivora. In cladistics, which reflect evolution, mammals are classified as endothermic amniotes, they are the only living Synapsida. The early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period around 300 million years ago, this group diverged from the sauropsid line that led to today's reptiles and birds; the line following the stem group Sphenacodontia split off several diverse groups of non-mammalian synapsids—sometimes referred to as mammal-like reptiles—before giving rise to the proto-mammals in the early Mesozoic era.
The modern mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, have been among the dominant terrestrial animal groups from 66 million years ago to the present. The basic body type is quadruped, most mammals use their four extremities for terrestrial locomotion. Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale—the largest animal on the planet. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. All modern mammals give birth to live young, except the five species of monotremes, which are egg-laying mammals; the most species-rich group of mammals, the cohort called placentals, have a placenta, which enables the feeding of the fetus during gestation. Most mammals are intelligent, with some possessing large brains, self-awareness, tool use. Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals and echolocation.
Mammals can organize themselves into fission-fusion societies and hierarchies—but can be solitary and territorial. Most mammals are polygynous. Domestication of many types of mammals by humans played a major role in the Neolithic revolution, resulted in farming replacing hunting and gathering as the primary source of food for humans; this led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, the development of the first civilizations. Domesticated mammals provided, continue to provide, power for transport and agriculture, as well as food and leather. Mammals are hunted and raced for sport, are used as model organisms in science. Mammals have been depicted in art since Palaeolithic times, appear in literature, film and religion. Decline in numbers and extinction of many mammals is driven by human poaching and habitat destruction deforestation. Mammal classification has been through several iterations since Carl Linnaeus defined the class.
No classification system is universally accepted. George Gaylord Simpson's "Principles of Classification and a Classification of Mammals" provides systematics of mammal origins and relationships that were universally taught until the end of the 20th century. Since Simpson's classification, the paleontological record has been recalibrated, the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself through the new concept of cladistics. Though field work made Simpson's classification outdated, it remains the closest thing to an official classification of mammals. 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, porcupines, beavers and other gnawing mammals. The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apes and lemurs. According to Mammal Species of the World, 5,416 species were identified in 2006.
These were grouped into 153 families and 29 orders. In 2008, the International Union for Conservation of Nature 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 extinct; the word "mammal" is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from the Latin mamma. In an influential 1988 paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes and therian m