The simians or Anthropoids are the monkeys, incl. apes, cladistically including: the New World monkeys or platyrrhines, the Catarrhine clade consisting of the Cercopithecidae and apes. The simians are sister to the tarsiers; the radiation occurred about 60 million years ago. 40 million years ago, simians from Afro-Arabia colonized South America, giving rise to the New World monkeys. The remaining simians split 25 million years ago into Cercopithecidae. In earlier classification, New World monkeys, Old World monkeys and humans—collectively known as simians or anthropoids—were grouped under Anthropoidea, while the strepsirrhines and tarsiers were grouped under the suborder "Prosimii". Under modern classification, the tarsiers and simians are grouped under the suborder Haplorhini while the strepsirrhines are placed in suborder Strepsirrhini. Strong genetic evidence for this is that five SINEs are common to all Haplorhines whilst absent in Strepsirrhines - one being coincidental between tarsiers and simians would be quite unlikely.
Despite this preferred taxonomic division, prosimian is still found in textbooks and the academic literature because of familiarity, a condition likened to the use of the metric system in the sciences and the use of customary units elsewhere in the United States. In Anthropoidea, evidence indicates that the Old and the New World primates went through parallel evolution. Primatology, paleoanthropology, other related fields are split on their usage of the synonymous infraorder names and Anthropoidea. According to Robert Hoffstetter, the term Simiiformes has priority over Anthropoidea because of the taxonomic term Simii by van der Hoeven, from which it is constructed, dates to 1833. In contrast, Anthropoidea by Mivart dates to 1864, while Simiiformes by Haeckel dates to 1866, leading to counterclaims of priority. Hoffstetter argued that Simiiformes is constructed like a proper infraorder name, whereas Anthropoidea ends in -oidea, reserved for superfamilies, he noted that Anthropoidea is too confused with "anthropoïdes", which translates to "apes" from several languages.
Extant simians are split into three distinct groups. The New World monkeys in parvorder Platyrrhini split from the rest of the simian line about 40 mya, leaving the parvorder Catarrhini occupying the Old World; this group split about 25 mya between the apes. There are some lines of extinct simian, either placed into Eosimiidae and sometimes in Amphipithecidae, thought to originate in the Early Oligocene. Additionally, Phileosimias is sometimes placed in the Eosimiidae and sometimes categorised separately; the following is the listing of the various simian families, their placement in the order Primates: Order Primates Suborder Strepsirrhini: non-tarsier prosimians Suborder Haplorhini: tarsiers + monkeys, including apes Infraorder Tarsiiformes Infraorder Simiiformes Parvorder Platyrrhini: New World monkeys Family Callitrichidae: marmosets and tamarins Family Cebidae: capuchins and squirrel monkeys Family Aotidae: night or owl monkeys Family Pitheciidae: titis and uakaris Family Atelidae: howler and woolly monkeys Parvorder Catarrhini Superfamily Cercopithecoidea Family Cercopithecidae Superfamily Hominoidea Family Hylobatidae: gibbons Family Hominidae: great apes, including humans †Amphipithecidae †EosimiidaeBelow is a cladogram with some of the extinct simian species with the more modern species emerging within the Eosimiidae.
The Simians originated in Asia. It is indicated how many million years ago the clades diverged into newer clades; the Ekgmowechashalidae are considered to be Strepsirrhini, not Haplorhini. A 2018 study places Eosimiidae as a sister to the crown haplorhini. In a section of their 2010 assessment of the evolution of anthropoids entitled'What Is An Anthropoid', Williams and Kirk set out a list of biological features that are common to all or most anthropoids, including genetic similarities, similarities in eye location and the muscles close to the eyes, internal similarities between ears, dental similarities, similarities on foot bone structure. Simia, Carl Linnaeus's original classification of these primates. BioMed Central Full text Gene conversion and purifying selection of a placenta-specific ERV-V envelope gene during simian evolution ADW Simiiformes Classification Taxonomy browser Late middle Eocene epoch of Libya yields earliest known radiation of African anthropoids Mouse-Sized Primates Shed Light on Human Origins
Crepuscular animals are those that are active during twilight. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daylight or the hours of darkness, respectively; the term is not precise, however, as some crepuscular animals may be active on a moonlit night or during an overcast day. The term matutinal is used for animals that are active only before sunrise, vespertine for those active only after sunset; the time of day an animal is active depends on a number of factors. Predators need to link their activities to times of day at which their prey is available, prey try to avoid the times when their principal predators are at large; the temperature at midday may be too high or at night too low. Some creatures may adjust their activities depending on local competition. Therefore, for many varied reasons, crepuscular activity may best meet an animal's requirements by compromise; the word crepuscular derives from the Latin crepusculum. Its sense accordingly differs from diurnal and nocturnal behavior, which peak during hours of daylight and darkness.
The distinction is not absolute however, because crepuscular animals may be active on a bright moonlit night or on a dull day. Some animals casually described. Special classes of crepuscular behaviour include matutinal and vespertine, denoting species active only in the dawn or only in the dusk, respectively; those that are active during both morning and evening twilight are said to have a bimodal activity pattern. The various patterns of activity are thought to be antipredator adaptations, though some could well be predatory adaptations. Many predators forage most intensively at night, whereas others are active at midday and see best in full sun. Thus, the crepuscular habit may both reduce predation pressure, thereby increasing the crepuscular populations, in consequence offer better foraging opportunities to predators that focus their attention on crepuscular prey until a new balance is struck; such shifting states of balance are found in ecology. Some predatory species adjust their habits in response to competition from other predators.
For example, the subspecies of short-eared owl that lives on the Galápagos Islands is active during the day, but on islands like Santa Cruz that are home to the Galapagos hawk, the owl is crepuscular. Apart from the relevance to predation, crepuscular activity in hot regions may be the most effective way of avoiding heat stress while capitalizing on available light. Many familiar mammal species are crepuscular, including some bats, housecats, stray dogs, ferrets, guinea pigs and rats. Other crepuscular mammals include jaguars, bobcats, red pandas, deer, sitatunga, chinchillas, the common mouse, squirrels, Australian wombats, quolls and marsupial gliders, spotted hyenas, African wild dogs. Snakes and lizards those in desert environments, may be crepuscular. Crepuscular birds include the common nighthawk, barn owl, owlet-nightjar, chimney swift, American woodcock, spotted crake, white-breasted waterhen. Many moths, beetles and other insects are crepuscular and vespertine. Cathemeral Crypsis Diurnality Nocturnality
Birds known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, a strong yet lightweight skeleton. Birds range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the world's most numerically-successful class of tetrapods, with ten thousand living species, more than half of these being passerines, sometimes known as perching birds. Birds have wings which are less developed depending on the species. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in flightless birds, including ratites and diverse endemic island species of birds; the digestive and respiratory systems of birds are uniquely adapted for flight. Some bird species of aquatic environments seabirds and some waterbirds, have further evolved for swimming; the fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier feathered dinosaurs within the theropod group, which are traditionally placed within the saurischian dinosaurs.
The closest living relatives of birds are the crocodilians. Primitive bird-like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid-Jurassic period, around 170 million years ago. Many of these early "stem-birds", such as Archaeopteryx, were not yet capable of powered flight, many retained primitive characteristics like toothy jaws in place of beaks, long bony tails. DNA-based evidence finds that birds diversified around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which killed off the pterosaurs and all the non-avian dinosaur lineages, but birds those in the southern continents, survived this event and migrated to other parts of the world while diversifying during periods of global cooling. This makes them the sole surviving dinosaurs according to cladistics; some birds corvids and parrots, are among the most intelligent animals. Many species annually migrate great distances. Birds are social, communicating with visual signals and bird songs, participating in such social behaviours as cooperative breeding and hunting and mobbing of predators.
The vast majority of bird species are monogamous for one breeding season at a time, sometimes for years, but for life. Other species have breeding systems that are polygynous or polyandrous. Birds produce offspring by laying eggs, they are laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching; some birds, such as hens, lay eggs when not fertilised, though unfertilised eggs do not produce offspring. Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs and feathers. Songbirds and other species are popular as pets. Guano is harvested for use as a fertiliser. Birds prominently figure throughout human culture. About 120–130 species have become extinct due to human activity since the 17th century, hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them.
Recreational birdwatching is an important part of the ecotourism industry. The first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae. Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system in use. Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda. Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1990s, Aves was most defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica. However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, is used by many scientists including adherents of the Phylocode system. Gauthier defined Aves to include only the crown group of the set of modern birds; this was done by excluding most groups known only from fossils, assigning them, instead, to the Avialae, in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.
Gauthier identified four different definitions for the same biological name "Aves", a problem. Gauthier proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below, he assigned other names to the other groups. Aves can mean all archosaurs closer to birds than to crocodiles Aves can mean those advanced archosaurs with feathers Aves can mean those feathered dinosaurs that fly Aves can mean the last common ancestor of all the living birds and all of its descendants (a "c
On Earth, daytime is the period of the day during which any given point in the world experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. During daytime, an observer sees indirect sunlight while in the shade, which includes cloud cover.'Day' is sometimes used instead of'daytime', in this case'day' will mean'the period of light between dawn and nightfall. However, in this context, in order to be clear "daytime" should be used distinguish it from "day" which refers to a 24-hour period. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star experience daytime of some sort, but this article discusses daytime on Earth. Half of the Earth is illuminated at any time by the Sun; the area subjected to direct illumination is exactly half the planet. The hemisphere of the Earth experiencing daytime at any given instant changes continuously as the planet rotates on its own axis.
The axis of the Earth's rotation is not perpendicular to the plane of its orbit around the Sun, so the length of the daytime period varies from one point on the planet to another. Additionally, since the axis of rotation is fixed in comparison to the stars, it moves with respect to the Sun as the planet orbits the star; this creates seasonal variations in the length of the daytime period at most points on the planet's surface. The period of daytime from the standpoint of a surface observer is defined as the period between sunrise, when the Earth's rotation towards the east first causes the Sun's disc to appear above the horizon, to sunset, when the continuing rotation of the Earth causes the Sun's disc to disappear below the horizon to the west; because the Sun is a luminous disc as seen from the Earth, rather than a point source of light and sunset are not instantaneous and the exact definition of both can vary with context. Additionally, the Earth's atmosphere further bends and diffuses light from the Sun and lengthens the period of sunrise and sunset.
For a certain period after sunset and before sunrise, indirect light from the Sun lightens the sky on Earth. Certain groups, such as Earthly astronomers, do not consider daytime to be ended until the Sun's disc is well below the Earth's horizon, because of this indirect illumination. Given that Earth's own axis of rotation is tilted about 23.5° to the line perpendicular to its orbital plane, called the ecliptic, the length of daytime varies with the seasons on the planet's surface, depending on the observer's latitude. Areas tilted toward the Sun are experiencing summer, their tilt toward the Sun leads to more than half of the day seeing daylight and warmer temperatures, due to the higher directness of solar rays, the longer period of daytime itself, less absorption of sunlight in the atmosphere. While increased daylight can have some effect on the higher temperatures in the summer, most of temperature rise results from the directness of the Sun, not the increased daylight; the high angles of the Sun causes the tropics to be warm, while low angles causes the polar regions to be cold.
The slight effect of daylight hours on average seasonal temperature can be seen with the poles and tropical regions. The poles are still cold during their respective summers, despite seeing 24 hours of daylight for six months, while the Equator remains warm throughout the year, with only 12 hours of daylight per day. Although the daytime length at the Equator remains 12 hours in all seasons, the duration at all other latitudes varies with the seasons. During the winter, daytime lasts shorter than 12 hours. Northern winter and southern summer concur, while northern summer and southern winter concur. At the Equator, the daytime period always lasts about 12 hours, regardless of season; as viewed from the Equator, the Sun always rises and sets vertically, following an apparent path nearly perpendicular to the horizon. Due to the axial tilt of Earth, Sun always lies within 23.5° north or south of the celestial equator, so the subsolar point always lies within the tropics. From the March equinox to the September equinox, the Sun rises within 23.5° north of due east, sets within 23.5° north of due west.
From the September equinox to the March equinox, the Sun rises within 23.5° south of due east and sets within 23.5° south of due west. The Sun's path lies in the northern half of the celestial sphere from the March equinox to the September equinox, but lies in the southern half of the celestial sphere from the September equinox to the March equinox. On the equinoxes, the equatorial Sun culminates at the zenith, passing directly overhead at solar noon; the fact that the equatorial Sun is always so close to the zenith at solar noon explains why the tropical zone contains the warmest regions on the planet overall. Additionally, the Equator sees the shortest sunrise or sunset because the Sun's path across the sky is so nearly perpendicular to the horizon. On the equinoxes, the solar disk takes only two minutes to traverse the horizon; the tropics occupy a zone of 23.5 ° south of the Equator. Within this zone, the Sun will p
Ethology is the scientific and objective study of animal behaviour with a focus on behaviour under natural conditions, viewing behaviour as an evolutionarily adaptive trait. Behaviourism is a term that describes the scientific and objective study of animal behaviour referring to measured responses to stimuli or trained behavioural responses in a laboratory context, without a particular emphasis on evolutionary adaptivity. Many naturalists have studied aspects of animal behaviour throughout history. Ethology has its scientific roots in the work of Charles Darwin and of American and German ornithologists of the late 19th and early 20th century, including Charles O. Whitman, Oskar Heinroth, Wallace Craig; the modern discipline of ethology is considered to have begun during the 1930s with the work of Dutch biologist Nikolaas Tinbergen and by Austrian biologists Konrad Lorenz and Karl von Frisch, joint awardees of the 1973 Nobel Prize in Physiology or Medicine. Ethology is a combination of laboratory and field science, with a strong relation to some other disciplines such as neuroanatomy and evolutionary biology.
Ethologists are interested in a behavioural process rather than in a particular animal group, study one type of behaviour, such as aggression, in a number of unrelated animals. Ethology is a growing field. Since the dawn of the 21st century, many aspects of animal communication, culture and sexuality that the scientific community long thought it understood have been re-examined, new conclusions reached. New fields, such as neuroethology, have developed. Understanding ethology or animal behaviour can be important in animal training. Considering the natural behaviours of different species or breeds enables the trainer to select the individuals best suited to perform the required task, it enables the trainer to encourage the performance of occurring behaviours and the discontinuance of undesirable behaviours. The term ethology derives from the Greek language: ἦθος, ethos meaning "character" and -λογία, -logia meaning "the study of"; the term was first popularized by American myrmecologist William Morton Wheeler in 1902.
Because ethology is considered a topic of biology, ethologists have been concerned with the evolution of behaviour and its understanding in terms of natural selection. In one sense, the first modern ethologist was Charles Darwin, whose 1872 book The Expression of the Emotions in Man and Animals influenced many ethologists, he pursued his interest in behaviour by encouraging his protégé George Romanes, who investigated animal learning and intelligence using an anthropomorphic method, anecdotal cognitivism, that did not gain scientific support. Other early ethologists, such as Charles O. Whitman, Oskar Heinroth, Wallace Craig and Julian Huxley, instead concentrated on behaviours that can be called instinctive, or natural, in that they occur in all members of a species under specified circumstances, their beginning for studying the behaviour of a new species was to construct an ethogram. This provided an objective, cumulative database of behaviour, which subsequent researchers could check and supplement.
Due to the work of Konrad Lorenz and Niko Tinbergen, ethology developed in continental Europe during the years prior to World War II. After the war, Tinbergen moved to the University of Oxford, ethology became stronger in the UK, with the additional influence of William Thorpe, Robert Hinde, Patrick Bateson at the Sub-department of Animal Behaviour of the University of Cambridge. In this period, ethology began to develop in North America. Lorenz and von Frisch were jointly awarded the Nobel Prize in Physiology or Medicine in 1973 for their work of developing ethology. Ethology is now a well-recognized scientific discipline, has a number of journals covering developments in the subject, such as Animal Behaviour, Animal Welfare, Applied Animal Behaviour Science, Animal Cognition, Behavioral Ecology and Journal of Ethology. In 1972, the International Society for Human Ethology was founded to promote exchange of knowledge and opinions concerning human behaviour gained by applying ethological principles and methods and published their journal, The Human Ethology Bulletin.
In 2008, in a paper published in the journal Behaviour, ethologist Peter Verbeek introduced the term "Peace Ethology" as a sub-discipline of Human Ethology, concerned with issues of human conflict, conflict resolution, war and peacekeeping behaviour. In 1972, the English ethologist John H. Crook distinguished comparative ethology from social ethology, argued that much of the ethology that had existed so far was comparative ethology—examining animals as individuals—whereas, in the future, ethologists would need to concentrate on the behaviour of social groups of animals and the social structure within them. In 1970, Robert Ardrey's book The Social Contract: A Personal Inquiry into the Evolutionary Sources of Order and Disorder was published; the book and study investigated animal behaviour and compared human behaviour to it as a similar phenomenon. E. O. Wilson's book Sociobiology: The New Synthesis appeared in 1975, since that time, the study of behaviour has been much more concerned with social aspects.
It has been driven by the stronger, but more sophisticated, Darwinism associated with Wilson, Robert Trivers, W. D. Hamilton; the related development of behavioural ecology has helped transform ethology. Furthermore, a substantial rapprochement with comparative psychology has occurred, so the modern scientific study of behaviour offers a mor
In ecology, crypsis is the ability of an animal to avoid observation or detection by other animals. It may be an antipredator adaptation. Methods include camouflage, subterranean lifestyle and mimicry. Crypsis can involve visual, olfactory, or auditory concealment; when it is visual, the term cryptic coloration a synonym for animal camouflage, is sometimes used, but many different methods of camouflage are employed by animals. There is a strong evolutionary pressure for animals to blend into their environment or conceal their shape, for prey animals to avoid predators and for predators to be able to avoid detection by prey. Exceptions include large herbivores without natural enemies, brilliantly colored birds that rely on flight to escape predators, venomous or otherwise powerfully armed animals with warning coloration. Cryptic animals include the tawny frogmouth, the tuatara, some jellyfish, the leafy sea dragon, the flounder. Methods of crypsis include camouflage and subterranean lifestyle. Camouflage can be achieved by a wide variety of methods, from disruptive coloration to transparency and some forms of mimicry in habitats like the open sea where there is no background.
As a strategy, crypsis is used by prey against predators. Crypsis applies to eggs and pheromone production. Crypsis can in principle involve olfactory, or auditory camouflage. Many animals have evolved so that they visually resemble their surroundings by using any of the many methods of natural camouflage that may match the color and texture of the surroundings and/or break up the visual outline of the animal itself; such animals may resemble rocks, twigs and bird droppings. Other methods including transparency and silvering are used by marine animals; some animals change color in changing environments seasonally, as in ermine and snowshoe hare, or far more with chromatophores in their integuments, as in chameleon and cephalopods such as squid. Countershading, the use of different colors on upper and lower surfaces in graduating tones from a light belly to a darker back, is common in the sea and on land, it is sometimes called Thayer's law, after the American artist Abbott Handerson Thayer, who published a paper on the form in 1896 that explained that countershading paints out shadows to make solid objects appear flat, reversing the way that artists use paint to make flat paintings contain solid objects.
Where the background is brighter than is possible with white pigment, counter-illumination in marine animals, such as squid, can use light to match the background. Some animals camouflage themselves with local materials; the decorator crabs attach plants, small stones, or shell fragments to their carapaces to provide camouflage that matches the local environment. Some species preferentially select stinging animals such as sea anemones or noxious plants, benefiting from aposematism as well as or instead of crypsis; some animals, in both terrestrial and aquatic environments, appear to camouflage their odor, which might otherwise attract predators. Numerous arthropods, both insects and spiders, mimic ants, whether to avoid predation, to hunt ants, or to trick the ants into feeding them. Pirate perch may exhibit chemical crypsis, making them undetectable to frogs and insects colonizing ponds; some insects, notably some Noctuid moths, some tiger moths, were theorized to defend themselves against predation by echolocating bats, both by passively absorbing sound with soft, fur-like body coverings and by creating sounds to mimic echoes from other locations or objects.
The active strategy was described as a "phantom echo" that might therefore represent "auditory crypsis", with alternative theories about interfering with the bats' echolocation. Subsequent research has provided evidence for only two functions of moth sounds, neither of which involve "auditory crypsis". Tiger moth species appear to cluster into two distinct groups. One type produces sounds as acoustic aposematism, warning the bats that the moths are unpalatable, or at least performing as acoustic mimics of unpalatable moths; the other type uses sonar jamming. In the latter type of moth, detailed analyses failed to support a "phantom echo" mechanism underlying sonar jamming, but instead pointed towards echo interference. There is a self-perpetuating co-evolution, or evolutionary arms race, between the perceptive abilities of animals attempting to detect the cryptic animal and the cryptic characteristics of the hiding species. Different aspects of crypsis and sensory abilities may be more or less pronounced in given predator-prey species pairs.
Zoologists need special methods to study cryptic animals, including biotelemetry techniques such as radio tracking and recapture, enclosures or exclosures. Cryptic animals tend to be overlooked in studies of biodiversity and ecological risk assessment. Dive Gallery: decorator crabs. Caterpillar that resembles bird droppings on leaves
The ostriches are a family, Struthionidae, of flightless birds. The two extant species of ostrich are the common ostrich and Somali ostrich, both in the genus Struthio, which contains several species known from Holocene fossils such as the Asian ostrich; the common ostrich is the more widespread of the two living species, is the largest living bird species. Other ostriches are among the largest bird species ever. Ostriches first appeared during the Miocene epoch, though various Paleocene and Oligocene fossils may belong to the family. Ostriches are classified in the ratite group of birds, all extant species of which are flightless, including the kiwis and rheas. Traditionally, the order Struthioniformes contained all the ratites. However, recent genetic analysis has found that the group is not monophyletic, as it is paraphyletic with respect to the tinamous, so the ostriches are classified as the only members of the order; the earliest fossils of ostrich-like birds are Paleocene taxa from Europe.
Palaeotis and Remiornis from the Middle Eocene and unspecified ratite remains are known from the Eocene and Oligocene of Europe and Africa. These may have been early relatives of the ostriches, but their status is questionable, they may in fact represent multiple lineages of flightless paleognaths; the African Eremopezus, when not considered a basal secretarybird or shoebill, is sometimes considered an ostrich relative or an "aepyornithid-like" taxon. Apart from these enigmatic birds, the fossil record of the ostriches continues with several species of the modern genus Struthio, which are known from the Early Miocene onwards. Several of these fossil forms are ichnotaxa and their association with those described from distinctive bones is contentious and in need of revision pending more good material. While the relationship of the African fossil species is comparatively straightforward, a large number of Asian species of ostriches have been described from fragmentary remains, their interrelationships and how they relate to the African ostriches are confusing.
In China, ostriches are known to have become extinct only around or after the end of the last ice age. Ostriches have co-existed with another lineage of the eogruids. Though Olson 1985 classified these birds as stem-ostriches, they are otherwise universally considered to be related to cranes, any similarities being the result of convergent evolution. Competition from ostriches has been suggested to have caused the extinction of the eogruids, though this has never been tested and both groups do co-exist in some sites. Order Struthioniformes Latham 1790 Family Struthionidae Vigors 1825 Genus?†Palaeotis Lambrecht 1928 †P. weigelti Lambrecht 1928 Genus?†Remiornis Lemoine, 1881 †Remiornis heberti Lemoine, 1881 Genus?†Eremopezus Andrews, 1904 †Eremopezus eocaenus Andrews, 1904 Genus Struthio Linnaeus 1758?†S. anderssoni Lowe 1931?†S. barbarus Arambourg 1979?†S. daberasensis Pickford, Senut & Dauphin 1995?†S. epoasticus Bonaparte?†S. kakesiensis Harrison & Msuya 2005?†S. karingarabensis Senut, Dauphin & Pickford 1998 †S. chersonensis Brandt 1873 †S. asiaticus Brodkorb 1863 †S. coppensi Mourer-Chauviré et al. 1996 †S. dmanisensis Burchak-Abramovich & Vekua 1990 †S. mongolicus †S. oldawayi Lowe 1933 †S. transcaucasicus Burchak-Abramovich & Vekua 1971 †S. wimani Lowe 1931 S. molybdophanes Reichenow 1883 S. camelus Linnaeus 1758 S. c. australis †S. c. syriacus Rothschild 1919 S. c. camelus Linnaeus 1758 S. c. massaicus Today ostriches are only found natively in the wild in Africa, where they occur in a range of open arid and semi-arid habitats such as savannas and the Sahel, both north and south of the equatorial forest zone.
The Somali ostrich occurs in the Horn of Africa, having evolved isolated from the common ostrich by the geographic barrier of the East African Rift. In some areas, the common ostrich's Masai subspecies occurs alongside the Somali ostrich, but they are kept from interbreeding by behavioral and ecological differences; the Arabian ostriches in Asia Minor and Arabia were hunted to extinction by the middle of the 20th century, in Israel attempts to introduce North African ostriches to fill their ecological role have failed. Escaped common ostriches in Australia have established feral populations