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126-577: In the seas, a novel major group of ammonoid cephalopods called clymeniids appeared, underwent tremendous diversification and spread worldwide, then just as suddenly went extinct. The beginning of the Famennian is marked by the final stages of a major extinction event , the Kellwasser Event , which is the largest component of the Late Devonian mass extinction. The end of the Famennian experiences

252-647: A diurnal pattern of activity, feeding from dawn to dusk, stopping sporadically to rest and chew their cud . Ideal pasture for sheep is not lawnlike grass, but an array of grasses , legumes and forbs . Types of land where sheep are raised vary widely, from pastures that are seeded and improved intentionally to rough, native lands. Common plants toxic to sheep are present in most of the world, and include (but are not limited to) cherry, some oaks and acorns, tomato, yew , rhubarb, potato, and rhododendron . Sheep are largely grazing herbivores, unlike browsing animals such as goats and deer that prefer taller foliage. With

378-670: A gestation period of about five months, and normal labor takes one to three hours. Although some breeds regularly throw larger litters of lambs, most produce single or twin lambs. During or soon after labor, ewes and lambs may be confined to small lambing jugs , small pens designed to aid both careful observation of ewes and to cement the bond between them and their lambs. Ovine obstetrics can be problematic. By selectively breeding ewes that produce multiple offspring with higher birth weights for generations, sheep producers have inadvertently caused some domestic sheep to have difficulty lambing; balancing ease of lambing with high productivity

504-470: A distinctive turnover of conodonts, particularly the last appearance of Palmatolepis bogartensis , the first appearance of Palmatolepis subperlobata , and an increase in the abundance of Palmatolepis ultima . It was previously defined by the start of the Palmatolepis triangularis conodont zone, but later studies showed that P. triangularis first appeared slightly later than the main conodont turnover in

630-472: A ewe and her direct descendants often move as a unit within large flocks. Sheep can become hefted to one particular local pasture (heft) so they do not roam freely in unfenced landscapes. Lambs learn the heft from ewes and if whole flocks are culled it must be retaught to the replacement animals. Flock behaviour in sheep is generally only exhibited in groups of four or more sheep; fewer sheep may not react as expected when alone or with few other sheep. Being

756-407: A few breeds that are predominantly used for milking. These sheep produce a higher quantity of milk and have slightly longer lactation curves. In the quality of their milk, the fat and protein content percentages of dairy sheep vary from non-dairy breeds, but lactose content does not. A last group of sheep breeds is that of fur or hair sheep , which do not grow wool at all. Hair sheep are similar to

882-411: A flat plane. The most fundamental difference in spiral form is how strongly successive whorls expand and overlap their predecessors. This can be inferred by the size of the umbilicus, the sunken-in inner part of the coil, exposing older and smaller whorls. Evolute shells have very little overlap, a large umbilicus, and many exposed whorls. Involute shells have strong overlap, a small umbilicus, and only

1008-468: A flock as it is herded between living sites. It has been reported that some sheep have apparently shown problem-solving abilities; a flock in West Yorkshire , England , allegedly found a way to get over cattle grids by rolling on their backs, although documentation of this has relied on anecdotal accounts. Sounds made by domestic sheep include bleats, grunts, rumbles and snorts. Bleating ("baaing")

1134-512: A general shape to ammonite tentacles. A contemporary study found an ammonite isolated body, offering for the first time a glimpse into these animals' organs. The smallest ammonoid was Maximites from the Upper Carboniferous . Adult specimens reached only 10 mm (0.39 in) in shell diameter. Few of the ammonites occurring in the lower and middle part of the Jurassic period reached

1260-420: A geographic envelope of the domestication center. One of the earliest animals to be domesticated for agricultural purposes, sheep are raised for fleeces , meat ( lamb, hogget or mutton ), and milk . A sheep's wool is the most widely used animal fiber, and is usually harvested by shearing . In Commonwealth countries, ovine meat is called lamb when from younger animals and mutton when from older ones; in

1386-519: A group continued through several major extinction events , although often only a few species survived. Each time, however, this handful of species diversified into a multitude of forms. Ammonite fossils became less abundant during the latter part of the Mesozoic , and although they seemingly survived the Cretaceous–Paleogene extinction event , all known Paleocene ammonite lineages are restricted to

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1512-479: A highly bred herding ability. Sheep are food-oriented, and association of humans with regular feeding often results in sheep soliciting people for food. Those who are moving sheep may exploit this behavior by leading sheep with buckets of feed. Sheep establish a dominance hierarchy through fighting, threats and competitiveness. Dominant animals are inclined to be more aggressive with other sheep, and usually feed first at troughs . Primarily among rams, horn size

1638-447: A month. Two fundamental preventive programs are maintaining good nutrition and reducing stress in the sheep. Restraint, isolation, loud noises, novel situations, pain, heat, extreme cold, fatigue and other stressors can lead to secretion of cortisol, a stress hormone, in amounts that may indicate welfare problems. Excessive stress can compromise the immune system. "Shipping fever" (pneumonic mannheimiosis, formerly called pasteurellosis)

1764-446: A much narrower face, sheep crop plants very close to the ground and can overgraze a pasture much faster than cattle. For this reason, many shepherds use managed intensive rotational grazing , where a flock is rotated through multiple pastures, giving plants time to recover. Paradoxically, sheep can both cause and solve the spread of invasive plant species . By disturbing the natural state of pasture, sheep and other livestock can pave

1890-434: A new pasture to avoid ingesting the same parasites. External sheep parasites include: lice (for different parts of the body), sheep keds , nose bots , sheep itch mites , and maggots . Keds are blood-sucking parasites that cause general malnutrition and decreased productivity, but are not fatal. Maggots are those of the bot fly and the blow-fly , commonly Lucilia sericata or its relative L. cuprina . Fly maggots cause

2016-428: A prey species, a sheep's system is adapted to hide the obvious signs of illness, to prevent being targeted by predators. However, some signs of ill health are obvious, with sick sheep eating little, vocalizing excessively, and being generally listless. Throughout history, much of the money and labor of sheep husbandry has aimed to prevent sheep ailments. Historically, shepherds often created remedies by experimentation on

2142-600: A prey species, the primary defense mechanism of sheep is to flee from danger when their flight zone is entered. Cornered sheep may charge and butt, or threaten by hoof stamping and adopting an aggressive posture. This is particularly true for ewes with newborn lambs. In regions where sheep have no natural predators, none of the native breeds of sheep exhibit a strong flocking behavior. Farmers exploit flocking behavior to keep sheep together on unfenced pastures such as hill farming , and to move them more easily. For this purpose shepherds may use herding dogs in this effort, with

2268-411: A result of limpets attaching themselves to the shells. However, the triangular formation of the holes, their size and shape, and their presence on both sides of the shells, corresponding to the upper and lower jaws, is more likely evidence of the bite of a medium-sized mosasaur preying upon ammonites. Some ammonites appear to have lived in cold seeps and even reproduced there. The chambered part of

2394-415: A result of selective breeding by humans. A few primitive breeds of sheep retain some of the characteristics of their wild cousins, such as short tails. Depending on breed, domestic sheep may have no horns at all (i.e. polled ), or horns in both sexes, or in males only. Most horned breeds have a single pair, but a few breeds may have several. Another trait unique to domestic sheep as compared to wild ovines

2520-476: A scent and indicate readiness through physical displays towards rams. In feral sheep, rams may fight during the rut to determine which individuals may mate with ewes. Rams, especially unfamiliar ones, will also fight outside the breeding period to establish dominance; rams can kill one another if allowed to mix freely. During the rut, even usually friendly rams may become aggressive towards humans due to increases in their hormone levels. After mating, sheep have

2646-558: A single horny plate or a pair of calcitic plates. In the past, these plates were assumed to serve in closing the opening of the shell in much the same way as an operculum , but more recently they are postulated to have been a jaw apparatus. The plates are collectively termed the aptychus or aptychi in the case of a pair of plates, and anaptychus in the case of a single plate. The paired aptychi were symmetric to one another and equal in size and appearance. Anaptychi are relatively rare as fossils. They are found representing ammonites from

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2772-637: A size exceeding 23 cm (9.1 in) in diameter. Much larger forms are found in the later rocks of the upper part of the Jurassic and the lower part of the Cretaceous, such as Titanites from the Portland Stone of Jurassic of southern England, which is often 53 cm (1.74 ft) in diameter, and Parapuzosia seppenradensis of the Cretaceous period of Germany, which is one of the largest-known ammonites, sometimes reaching 2 m (6.6 ft) in diameter. The largest-documented North American ammonite

2898-497: A slow rate of growth. Long wool sheep are most valued for crossbreeding to improve the attributes of other sheep types. For example: the American Columbia breed was developed by crossing Lincoln rams (a long wool breed) with fine-wooled Rambouillet ewes. Coarse or carpet wool sheep are those with a medium to long length wool of characteristic coarseness. Breeds traditionally used for carpet wool show great variability, but

3024-810: A smaller but still quite severe extinction event, the Hangenberg Event . A brief episode of glaciation, possibly linked to the Hangenberg event, occurred during the late Famennian, the first in a series of short glaciations that preceded the Late Palaeozoic ice age of the Carboniferous and Permian periods. The International Commission on Stratigraphy divides the Famennian into four informal substages based primarily on conodont zonation. The Famennian corresponds to four historical subdivisions in German stratigraphy:

3150-815: A study published in Nature in 2001, Kenneth M. Kendrick and others reported; "Sheep recognize and are attracted to individual sheep and humans by their faces, as they possess similar specialized neural systems in the temporal and frontal lobes  ... individual sheep can remember 50 other different sheep faces for over 2 years". In addition to long-term facial recognition of individuals, sheep can also differentiate emotional states through facial characteristics. If worked with patiently, sheep may learn their names, and many sheep are trained to be led by halter for showing and other purposes. Sheep have also responded well to clicker training . Sheep have been used as pack animals; Tibetan nomads distribute baggage equally throughout

3276-422: A tendency to congregate close to other members of a flock, although this behavior varies with breed, and sheep can become stressed when separated from their flock members. During flocking, sheep have a strong tendency to follow, and a leader may simply be the first individual to move. Relationships in flocks tend to be closest among related sheep: in mixed-breed flocks, subgroups of the same breed tend to form, and

3402-407: A waste product or a scent marker to help lost sheep find their flock, have also been proposed. Sheep and goats are closely related: both are in the subfamily Caprinae . However, they are separate species, so hybrids rarely occur and are always infertile. A hybrid of a ewe and a buck (a male goat) is called a sheep-goat hybrid , known as geep . Visual differences between sheep and goats include

3528-415: A well-focused retinal image of objects in both the middle and long distance. Because sheep eyes have no accommodation , one might expect the image of very near objects to be blurred, but a rather clear near image could be provided by the tapetum and large retinal image of the sheep's eye, and adequate close vision may occur at muzzle length. Good depth perception, inferred from the sheep's sure-footedness,

3654-615: A wide scale, and were an important agent in the spread of sheep raising. Pliny the Elder , in his Natural History ( Naturalis Historia ), speaks at length about sheep and wool. European colonists spread the practice to the New World from 1493 onwards. Domestic sheep are relatively small ruminants, usually with a crimped hair called wool and often with horns forming a lateral spiral . They differ from their wild relatives and ancestors in several respects, having become uniquely neotenic as

3780-458: Is Baculites , which has a nearly straight shell convergent with the older orthocone nautiloids. Still other species' shells are coiled helically (in two dimensions), similar in appearance to some gastropods (e.g., Turrilites and Bostrychoceras ). Some species' shells are even initially uncoiled, then partially coiled, and finally straight at maturity (as in Australiceras ). Perhaps

3906-506: Is Parapuzosia bradyi from the Cretaceous, with specimens measuring 137 cm (4.5 ft) in diameter. Starting from the mid-Devonian, ammonoids were extremely abundant, especially as ammonites during the Mesozoic era. Many genera evolved and ran their course quickly, becoming extinct in a few million years. Due to their rapid evolution and widespread distribution, ammonoids are used by geologists and paleontologists for biostratigraphy . They are excellent index fossils , and it

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4032-496: Is hay , often during the winter months. The ability to thrive solely on pasture (even without hay) varies with breed, but all sheep can survive on this diet. Also included in some sheep's diets are minerals , either in a trace mix or in licks . Feed provided to sheep must be specially formulated, as most cattle, poultry, pig, and even some goat feeds contain levels of copper that are lethal to sheep. The same danger applies to mineral supplements such as salt licks . Sheep follow

4158-409: Is a dominant trait it spread quickly. However, colored sheep do appear in many modern breeds, and may even appear as a recessive trait in white flocks. While white wool is desirable for large commercial markets, there is a niche market for colored fleeces, mostly for handspinning . The nature of the fleece varies widely among the breeds, from dense and highly crimped, to long and hairlike. There

4284-539: Is a disease of particular concern, that can occur as a result of stress, notably during transport and (or) handling. Pain, fear and several other stressors can cause secretion of epinephrine (adrenaline). Considerable epinephrine secretion in the final days before slaughter can adversely affect meat quality (by causing glycogenolysis, removing the substrate for normal post-slaughter acidification of meat) and result in meat becoming more susceptible to colonization by spoilage bacteria. Because of such issues, low-stress handling

4410-485: Is a factor in the flock hierarchy. Rams with different size horns may be less inclined to fight to establish the dominance order, while rams with similarly sized horns are more so. Merinos have an almost linear hierarchy whereas there is a less rigid structure in Border Leicesters when a competitive feeding situation arises. In sheep, position in a moving flock is highly correlated with social dominance, but there

4536-499: Is a highly contagious and often fatal viral disease affecting sheep and goats. Sheep may also be affected by primary or secondary photosensitization. Tetanus can also afflict sheep through wounds from shearing , docking , castration , or vaccination. The organism also can be introduced into the reproductive tract by unsanitary humans who assist ewes during lambing. A few sheep conditions are transmissible to humans. Orf (also known as scabby mouth, contagious ecthyma or soremouth)

4662-476: Is a skin disease leaving lesions that is transmitted through skin-to-skin contact. Cutaneous anthrax is also called woolsorter's disease, as the spores can be transmitted in unwashed wool. More seriously, the organisms that can cause spontaneous enzootic abortion in sheep are easily transmitted to pregnant women. Also of concern are the prion disease scrapie and the virus that causes foot-and-mouth disease (FMD), as both can devastate flocks. The latter poses

4788-677: Is commonly given at an age of about 10 to 12 weeks; i.e. when the concentration of maternal antibodies passively acquired via colostrum is expected to have fallen low enough to permit development of active immunity. Ewes are often revaccinated annually about 3 weeks before lambing, to provide high antibody concentrations in colostrum during the first several hours after lambing. Ram lambs that will either be slaughtered or separated from ewes before sexual maturity are not usually castrated. Objections to all these procedures have been raised by animal rights groups, but farmers defend them by saying they save money, and inflict only temporary pain. Sheep are

4914-414: Is essential in sheep management. Avoiding poisoning is also important; common poisons are pesticide sprays, inorganic fertilizer , motor oil , as well as radiator coolant containing ethylene glycol. Common forms of preventive medication for sheep are vaccinations and treatments for parasites . Both external and internal parasites are the most prevalent malady in sheep, and are either fatal, or reduce

5040-612: Is found. In general, they appear to have inhabited the upper 250 meters of the water column. Many of them (such as Oxynoticeras ) are thought to have been good swimmers, with flattened, discus-shaped, streamlined shells, although some ammonoids were less effective swimmers and were likely to have been slow-swimming bottom-dwellers. Synchrotron analysis of an aptychophoran ammonite revealed remains of isopod and mollusc larvae in its buccal cavity, indicating at least this kind of ammonite fed on plankton . They may have avoided predation by squirting ink , much like modern cephalopods; ink

5166-419: Is known about their way of life. Their soft body parts are very rarely preserved in any detail. Nonetheless, much has been worked out by examining ammonoid shells and by using models of these shells in water tanks. Many ammonoids probably lived in the open water of ancient seas, rather than at the sea bottom, because their fossils are often found in rocks laid down under conditions where no bottom-dwelling life

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5292-438: Is no definitive study to show consistent voluntary leadership by an individual sheep. Sheep are frequently thought of as unintelligent animals . Their flocking behavior and quickness to flee and panic can make shepherding a difficult endeavor for the uninitiated. Despite these perceptions, a University of Illinois monograph on sheep reported their intelligence to be just below that of pigs and on par with that of cattle. In

5418-422: Is occasionally preserved in fossil specimens. The soft body of the creature occupied the largest segments of the shell at the end of the coil. The smaller earlier segments were walled off and the animal could maintain its buoyancy by filling them with gas. Thus, the smaller sections of the coil would have floated above the larger sections. Many ammonite shells have been found with round holes once interpreted as

5544-467: Is often possible to link the rock layer in which they are found to specific geologic time periods . Due to their free-swimming and/or free-floating habits, ammonites often happened to live directly above seafloor waters so poor in oxygen as to prevent the establishment of animal life on the seafloor. When upon death the ammonites fell to this seafloor and were gradually buried in accumulating sediment, bacterial decomposition of these corpses often tipped

5670-614: Is often preserved. This type of preservation is found in ammonites such as Hoplites from the Cretaceous Gault clay of Folkestone in Kent, England. The Cretaceous Pierre Shale formation of the United States and Canada is well known for the abundant ammonite fauna it yields, including Baculites , Placenticeras , Scaphites , Hoploscaphites and Jeletzkytes , as well as many uncoiled forms. Many of these also have much or all of

5796-477: Is one of the dilemmas of sheep breeding. In the case of any such problems, those present at lambing may assist the ewe by extracting or repositioning lambs. After the birth, ewes ideally break the amniotic sac (if it is not broken during labor), and begin licking clean the lamb. Most lambs will begin standing within an hour of birth. In normal situations, lambs nurse after standing, receiving vital colostrum milk. Lambs that either fail to nurse or are rejected by

5922-458: Is their wide variation in color. Wild sheep are largely variations of brown hues, and variation within species is extremely limited. Colors of domestic sheep range from pure white to dark chocolate brown, and even spotted or piebald . Sheep keepers also sometimes artificially paint "smit marks" onto their sheep in any pattern or color for identification. Selection for easily dyeable white fleeces began early in sheep domestication, and as white wool

6048-433: Is then passed into the rumen , via the reticulum . The rumen is a 19- to 38-liter (5 to 10 gallon) organ in which feed is fermented . The fermenting organisms include bacteria, fungi, and protozoa. (Other important rumen organisms include some archaea, which produce methane from carbon dioxide. ) The bolus is periodically regurgitated back to the mouth as cud for additional chewing and salivation . After fermentation in

6174-527: Is thought to be because the female required a larger body size for egg production. A good example of this sexual variation is found in Bifericeras from the early part of the Jurassic period of Europe . Only recently has sexual variation in the shells of ammonites been recognized. The macroconch and microconch of one species were often previously mistaken for two closely related but different species occurring in

6300-692: Is used mostly for contact communication, especially between dam and lambs, but also at times between other flock members. The bleats of individual sheep are distinctive, enabling the ewe and her lambs to recognize each other's vocalizations. Vocal communication between lambs and their dam declines to a very low level within several weeks after parturition. A variety of bleats may be heard, depending on sheep age and circumstances. Apart from contact communication, bleating may signal distress, frustration or impatience; however, sheep are usually silent when in pain. Isolation commonly prompts bleating by sheep. Pregnant ewes may grunt when in labor. Rumbling sounds are made by

6426-489: Is variation of wool type and quality even among members of the same flock, so wool classing is a step in the commercial processing of the fibre. Depending on breed, sheep show a range of heights and weights. Their rate of growth and mature weight is a heritable trait that is often selected for in breeding. Ewes typically weigh between 45 and 100 kilograms (100 and 220 lb), and rams between 45 and 160 kilograms (100 and 350 lb). When all deciduous teeth have erupted,

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6552-433: Is widespread, and is the main impediment to certified organic farming with sheep. Many breeders take a variety of preventive measures to ward off problems. The first is to ensure all sheep are healthy when purchased. Many buyers avoid outlets known to be clearing houses for animals culled from healthy flocks as either sick or simply inferior. This can also mean maintaining a closed flock, and quarantining new sheep for

6678-569: The Abrahamic traditions. In both ancient and modern religious ritual, sheep are used as sacrificial animals . The exact line of descent from wild ancestors to domestic sheep is unclear. The most common hypothesis states that Ovis aries is descended from the Asiatic ( O. gmelini ) species of mouflon ; the European mouflon ( Ovis aries musimon ) is a direct descendant of this population. Sheep were among

6804-629: The Devonian ( circa 409 million years ago (Mya)) and became extinct shortly after Cretaceous (66 Mya). The classification of ammonoids is based in part on the ornamentation and structure of the septa comprising their shells' gas chambers. The Ammonoidea can be divided into six orders, listed here starting with the most primitive and going to the more derived: In some classifications, these are left as suborders, included in only three orders: Goniatitida , Ceratitida and Ammonitida . The Treatise on Invertebrate Paleontology (Part L, 1957) divides

6930-739: The Paleocene epoch (65–61 Ma). Goniatites, which were a dominant component of Early and Middle Permian faunas, became rare in the Late Permian, and no goniatite is thought to have crossed into the Triassic. Ceratitida originated during the Middle Permian, likely from the Daraelitidae , and radiated in the Late Permian. In the aftermath of the Permian–Triassic extinction event , Ceratitids represent

7056-629: The Solnhofen Limestone , their soft-part record is surprisingly sparse. Beyond a tentative ink sac and possible digestive organs, no soft parts were known until 2021. When neutron imaging was used on a fossil found in 1998, part of the musculature became visible and showed they were able to retract themselves into the shell for protection, and that the retractor muscles and hyponome that work together to enable jet propulsion in nautilus worked independently in ammonites. The reproductive organs show possible traces of spermatophores, which would support

7182-433: The buoyancy of the shell and thereby rise or descend in the water column. A primary difference between ammonites and nautiloids is the siphuncle of ammonites (excepting Clymeniina ) runs along the ventral periphery of the septa and camerae (i.e., the inner surface of the outer axis of the shell), while the siphuncle of nautiloids runs more or less through the center of the septa and camerae. One feature found in shells of

7308-505: The dental formula for sheep is either 0.0.3.3 4.0.3.3 or 0.0.3.3 3.1.3.3 There is a large diastema between the incisors and the molars . In the first few years of life one can calculate the age of sheep from their front teeth, as a pair of milk teeth is replaced by larger adult teeth each year, the full set of eight adult front teeth being complete at about four years of age. The front teeth are then gradually lost as sheep age, making it harder for them to feed and hindering

7434-430: The order Artiodactyla , the even-toed ungulates . Numbering a little over one billion, domestic sheep are also the most numerous species of sheep. An adult female is referred to as a ewe ( / j uː / yoo ), an intact male as a ram , occasionally a tup , a castrated male as a wether , and a young sheep as a lamb . Sheep are most likely descended from the wild mouflon of Europe and Asia, with Iran being

7560-454: The rut , whereas rams do not. The domestic sheep is a multi-purpose animal, and the more than 200 breeds now in existence were created to serve these diverse purposes. Some sources give a count of a thousand or more breeds, but these numbers cannot be verified, according to some sources. However, several hundred breeds of sheep have been identified by the Food and Agriculture Organization of

7686-653: The topography for which the breed has been developed. This last point is especially stressed in the UK, where breeds are described as either upland (hill or mountain) or lowland breeds. A sheep may also be of a fat-tailed type , which is a dual-purpose sheep common in Africa and Asia with larger deposits of fat within and around its tail. Breeds are often categorized by the type of their wool. Fine wool breeds are those that have wool of great crimp and density, which are preferred for textiles. Most of these were derived from Merino sheep, and

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7812-423: The 20th and 21st centuries, a minority of sheep owners have turned to alternative treatments such as homeopathy , herbalism and even traditional Chinese medicine to treat sheep veterinary problems. Despite some favorable anecdotal evidence , the effectiveness of alternative veterinary medicine has been met with skepticism in scientific journals . The need for traditional anti-parasite drugs and antibiotics

7938-695: The Ammonoidea, regarded simply as an order, into eight suborders, the Anarcestina, Clymeniina, Goniatitina and Prolecanitina from the Paleozoic; the Ceratitina from the Triassic; and the Ammonitina, Lytoceratina and Phylloceratina from the Jurassic and Cretaceous. In subsequent taxonomies, these are sometimes regarded as orders within the subclass Ammonoidea. Because ammonites and their close relatives are extinct, little

8064-535: The Devonian period through those of the Cretaceous period. Calcified aptychi only occur in ammonites from the Mesozoic era. They are almost always found detached from the shell, and are only very rarely preserved in place. Still, sufficient numbers have been found closing the apertures of fossil ammonite shells as to leave no doubt as to their identity as part of the anatomy of an ammonite. Large numbers of detached aptychi occur in certain beds of rock (such as those from

8190-458: The Elder ( d. 79 AD near Pompeii) called fossils of these animals ammonis cornua (" horns of Ammon ") because the Egyptian god Ammon ( Amun ) was typically depicted wearing rams' horns. Often, the name of an ammonite genus ends in - ceras , which is from κέρας ( kéras ) meaning "horn". Ammonites (subclass Ammonoidea) can be distinguished by their septa, the dividing walls that separate

8316-541: The GSSP. A 2012 ICS timescale based on rough radioisotopic records estimated the Famennian began around 372.2 ± 1.6 Ma, and ended at 358.9 ± 0.4 Ma. In 2020 this was revised to a start at 371.1 ± 1.1 Ma and an end at 359.3 ± 0.3 Ma. Ammonoid Ammonoids are extinct spiral shelled cephalopods comprising the subclass Ammonoidea . They are more closely related to living coleoids (i.e., octopuses , squid and cuttlefish ) than they are to shelled nautiloids (such as

8442-913: The Jacobson's organ) to sense the pheromones of ewes and detect when they are in estrus . The ewe uses her vomeronasal organ for early recognition of her neonate lamb. Sheep follow a similar reproductive strategy to other herd animals. A group of ewes is generally mated by a single ram, who has either been chosen by a breeder or (in feral populations) has established dominance through physical contest with other rams. Most sheep are seasonal breeders , although some are able to breed year-round. Ewes generally reach sexual maturity at six to eight months old, and rams generally at four to six months. However, there are exceptions. For example, Finnsheep ewe lambs may reach puberty as early as 3 to 4 months, and Merino ewes sometimes reach puberty at 18 to 20 months. Ewes have estrus cycles about every 17 days, during which they emit

8568-510: The Mesozoic in the Alps ). These rocks are usually accumulated at great depths. The modern Nautilus lacks any calcitic plate for closing its shell, and only one extinct nautiloid genus is known to have borne anything similar. Nautilus does, however, have a leathery head shield (the hood) which it uses to cover the opening when it retreats inside. There are many forms of aptychus, varying in shape and

8694-732: The Nehdenian, Hembergian, Dasbergian, and Wocklumian (from oldest to youngest). However, these are based solely on ammonoid zonation and do not precisely correspond to the informal ICS subdivisions. The Uppermost Famennian substage (approximating the Wocklumian) is also known as the Strunian in the Ardennes region. North American subdivisions of the Famennian include the Chautauquan, Canadaway, Conneaut, Conneautan, Conewango and Conewangan. The Famennian Stage

8820-591: The UN (FAO), with the estimated number varying somewhat from time to time: e.g. 863 breeds as of 1993, 1314 breeds as of 1995 and 1229 breeds as of 2006. (These numbers exclude extinct breeds, which are also tallied by the FAO.) For the purpose of such tallies, the FAO definition of a breed is "either a subspecific group of domestic livestock with definable and identifiable external characteristics that enable it to be separated by visual appraisal from other similarly defined groups within

8946-418: The United States, meat from both older and younger animals is usually called lamb. Sheep continue to be important for wool and meat today, and are also occasionally raised for pelts , as dairy animals, or as model organisms for science. Sheep husbandry is practised throughout the majority of the inhabited world, and has been fundamental to many civilizations. In the modern era, Australia , New Zealand ,

9072-440: The ammonite shell is called a phragmocone . It contains a series of progressively larger chambers, called camerae (sing. camera) that are divided by thin walls called septa (sing. septum). Only the last and largest chamber, the body chamber , was occupied by the living animal at any given moment. As it grew, it added newer and larger chambers to the open end of the coil. Where the outer whorl of an ammonite shell largely covers

9198-469: The animal's life; additional shell layers covered it. The majority of ammonoid specimens, especially those of the Paleozoic era, are preserved only as internal molds; the outer shell (composed of aragonite ) has been lost during the fossilization process. Only in these internal-mould specimens can the suture lines be observed; in life, the sutures would have been hidden by the outer shell. The ammonoids as

9324-415: The aperture) and lobes ("valleys" which point away from the aperture). The suture line has four main regions. The external or ventral region refers to sutures along the lower (outer) edge of the shell, where the left and right suture lines meet. The external (or ventral) saddle, when present, lies directly on the lower midline of the shell. As a result, it is often called the median saddle. On suture diagrams

9450-449: The basis of these tendencies. The dominance hierarchy of sheep and their natural inclination to follow a leader to new pastures were the pivotal factors in sheep being one of the first domesticated livestock species. Furthermore, in contrast to the red deer and gazelle (two other ungulates of primary importance to meat production in prehistoric times), sheep do not defend territories although they do form home ranges . All sheep have

9576-418: The beard of goats and divided upper lip of sheep. Sheep tails also hang down, even when short or docked , while the short tails of goats are held upwards. Also, sheep breeds are often naturally polled (either in both sexes or just in the female), while naturally polled goats are rare (though many are polled artificially). Males of the two species differ in that buck goats acquire a unique and strong odor during

9702-454: The breed continues to dominate the world sheep industry. Downs breeds have wool between the extremes, and are typically fast-growing meat and ram breeds with dark faces. Some major medium wool breeds, such as the Corriedale , are dual-purpose crosses of long and fine-wooled breeds and were created for high-production commercial flocks. Long wool breeds are the largest of sheep, with long wool and

9828-571: The center of the whorl that they are covered up by succeeding whorls are labelled internal (or dorsal) lobes and saddles. Three major types of suture patterns are found in the Ammonoidea: The siphuncle in most ammonoids is a narrow tubular structure that runs along the shell's outer rim, known as the venter, connecting the chambers of the phragmocone to the body or living chamber. This distinguishes them from living nautiloides ( Nautilus and Allonautilus ) and typical Nautilida , in which

9954-419: The chambers in the phragmocone, by the nature of their sutures where the septa join the outer shell wall, and in general by their siphuncles . Ammonoid septa characteristically have bulges and indentations and are to varying degrees convex when seen from the front, distinguishing them from nautiloid septa, which are typically simple concave, dish-shaped structures. The topology of the septa, especially around

10080-499: The chief requirement is a wool that will not break down under heavy use (as would that of the finer breeds). As the demand for carpet-quality wool declines, some breeders of this type of sheep are attempting to use a few of these traditional breeds for alternative purposes. Others have always been primarily meat-class sheep. A minor class of sheep are the dairy breeds. Dual-purpose breeds that may primarily be meat or wool sheep are often used secondarily as milking animals, but there are

10206-399: The decline of localized family farms , many breeds of sheep are in danger of extinction. The Rare Breeds Survival Trust of the UK lists 22 native breeds as having only 3,000 registered animals (each), and The Livestock Conservancy lists 14 as either "critical" or "threatened". Preferences for breeds with uniform characteristics and fast growth have pushed heritage (or heirloom) breeds to

10332-419: The delicate balance of local redox conditions sufficiently to lower the local solubility of minerals dissolved in the seawater, notably phosphates and carbonates . The resulting spontaneous concentric precipitation of minerals around a fossil, a concretion , is responsible for the outstanding preservation of many ammonite fossils. When ammonites are found in clays , their original mother-of-pearl coating

10458-466: The dominant group of Triassic ammonites. Sheep Ovis guineensis Linnaeus, 1758 Ovis strepsiceros Linnaeus, 1758 Sheep ( pl. : sheep) or domestic sheep ( Ovis aries ) are a domesticated , ruminant mammal typically kept as livestock . Although the term sheep can apply to other species in the genus Ovis , in everyday usage it almost always refers to domesticated sheep. Like all ruminants, sheep are members of

10584-774: The earliest woven wool garments have been dated to two to three thousand years later. Sheep husbandry spread quickly in Europe. Excavations show that in about 6000 BC, during the Neolithic period of prehistory, the Castelnovien people, living around Châteauneuf-les-Martigues near present-day Marseille in the south of France, were among the first in Europe to keep domestic sheep. Practically from its inception, ancient Greek civilization relied on sheep as primary livestock, and were even said to name individual animals. Ancient Romans kept sheep on

10710-472: The early domesticated sheep kept before woolly breeds were developed, and are raised for meat and pelts. Some modern breeds of hair sheep, such as the Dorper , result from crosses between wool and hair breeds. For meat and hide producers, hair sheep are cheaper to keep, as they do not need shearing. Hair sheep are also more resistant to parasites and hot weather. With the modern rise of corporate agribusiness and

10836-728: The ewe require help to survive, such as bottle-feeding or fostering by another ewe. Most lambs begin life being born outdoors. After lambs are several weeks old, lamb marking ( ear tagging , docking , mulesing , and castrating ) is carried out. Vaccinations are usually carried out at this point as well. Ear tags with numbers are attached, or ear marks are applied, for ease of later identification of sheep. Docking and castration are commonly done after 24 hours (to avoid interference with maternal bonding and consumption of colostrum) and are often done not later than one week after birth, to minimize pain, stress, recovery time and complications. The first course of vaccinations (commonly anti-clostridial)

10962-403: The extremely destructive condition of flystrike . Flies lay their eggs in wounds or wet, manure-soiled wool; when the maggots hatch they burrow into a sheep's flesh, eventually causing death if untreated. In addition to other treatments, crutching (shearing wool from a sheep's rump) is a common preventive method. Some countries allow mulesing , a practice that involves stripping away the skin on

11088-418: The face, and some have facial wool (if any) confined to the poll and or the area of the mandibular angle; the wide angles of peripheral vision apply to these breeds. A few breeds tend to have considerable wool on the face; for some individuals of these breeds, peripheral vision may be greatly reduced by "wool blindness", unless recently shorn about the face. Sheep have poor depth perception ; shadows and dips in

11214-547: The farm. In some developed countries, including the United States, sheep lack the economic importance for drug companies to perform expensive clinical trials required to approve more than a relatively limited number of drugs for ovine use. However, extra-label drug use in sheep production is permitted in many jurisdictions, subject to certain restrictions. In the US, for example, regulations governing extra-label drug use in animals are found in 21 CFR (Code of Federal Regulations) Part 530. In

11340-841: The first animals to be domesticated by humankind (although the domestication of dogs probably took place 10 to 20 thousand years earlier); the domestication date is estimated to fall between 11,000 and 9000 BC in Mesopotamia and possibly around 7000 BC in Mehrgarh in the Indus Valley. The rearing of sheep for secondary products, and the resulting breed development, began in either southwest Asia or western Europe. Initially, sheep were kept solely for meat, milk and skins. Archaeological evidence from statuary found at sites in Iran suggests that selection for woolly sheep may have begun around 6000 BC, and

11466-459: The first heteromorph ammonoid fossils belongs to the genus Rhabdoceras. The three other heteromorphic genera were Hannaoceras, Cochloceras and Choristoceras. All of them went extinct at the end of Triassic. In the Jurassic an uncoiled shell was found in the Spiroceratoidea, but by the end of Cretaceous the only heteromorph ammonites remaining belonged to the suborder Ancyloceratina. One example

11592-529: The ground may cause sheep to baulk. In general, sheep have a tendency to move out of the dark and into well-lit areas, and prefer to move uphill when disturbed. Sheep also have an excellent sense of smell, and, like all species of their genus, have scent glands just in front of the eyes, and interdigitally on the feet. The purpose of these glands is uncertain, but those on the face may be used in breeding behaviors. The foot glands might also be related to reproduction, but alternative functions, such as secretion of

11718-537: The health and productivity of the animal. For this reason, domestic sheep on normal pasture begin to slowly decline from four years on, and the life expectancy of a sheep is 10 to 12 years, though some sheep may live as long as 20 years. Sheep have good hearing, and are sensitive to noise when being handled. Sheep have horizontal slit-shaped pupils, with excellent peripheral vision ; with visual fields of about 270° to 320°, sheep can see behind themselves without turning their heads. Many breeds have only short hair on

11844-451: The hoof, such as foot rot and foot scald may occur, and are treated with footbaths and other remedies. Foot rot is present in over 97% of flocks in the UK. These painful conditions cause lameness and hinder feeding. Ovine Johne's disease is a wasting disease that affects young sheep. Bluetongue disease is an insect-borne illness causing fever and inflammation of the mucous membranes . Ovine rinderpest (or peste des petits ruminants )

11970-503: The hypothesis that the microconchs were males. They likely bore a radula and beak, a marginal siphuncle and ten arms. They operated by direct development with sexual reproduction, were carnivorous, and had a crop for food storage. They are unlikely to have dwelt in fresh or brackish water. Many ammonites were likely filter feeders , so adaptations associated with this lifestyle like sieves probably occurred. A 2021 study found ammonite specimens with preserved hook-like suckers, providing

12096-511: The largest and most recent whorls are exposed. Shell structure can be broken down further by the width of the shell, with implications for hydrodynamic efficiency. Major shell forms include: Ammonites vary greatly in the ornamentation (surface relief) of their shells. Some may be smooth and relatively featureless, except for growth lines, resembling that of the modern Nautilus . In others, various patterns of spiral ridges, ribs, nodes, or spines are presented. This type of complex ornamentation of

12222-427: The living Nautilus ). The earliest ammonoids appeared during the Devonian , with the last species vanishing during or soon after the Cretaceous–Paleogene extinction event . They are often called ammonites , which is most frequently used for members of the order Ammonitida , the only remaining group of ammonoids from the Jurassic up until their extinction. Ammonites are excellent index fossils , and linking

12348-429: The margins of the sheep industry. Those that remain are maintained through the efforts of conservation organizations, breed registries, and individual farmers dedicated to their preservation. Sheep are herbivorous . Most breeds prefer to graze on grass and other short roughage , avoiding the taller woody parts of plants that goats readily consume. Both sheep and goats use their lips and tongues to select parts of

12474-445: The measurements were limited by wool, although photographs of the experiments indicate that only limited facial wool regrowth had occurred since shearing. In addition to facial wool (in some breeds), visual field limitations can include ears and (in some breeds) horns, so the visual field can be extended by tilting the head. Sheep eyes exhibit very low hyperopia and little astigmatism . Such visual characteristics are likely to produce

12600-418: The median saddle is supplied with an arrow which points towards the aperture. The median saddle is edged by fairly small external (or ventral) lobes. The earliest ammonoids lacked a median saddle and instead had a single midline ventral lobe, which in later forms is split into two or more components. The lateral region involves the first saddle and lobe pair past the external region as the suture line extends up

12726-432: The modern Nautilus is the variation in the shape and size of the shell according to the sex of the animal, the shell of the male being slightly smaller and wider than that of the female. This sexual dimorphism is thought to be an explanation for the variation in size of certain ammonite shells of the same species, the larger shell (the macroconch ) being female, and the smaller shell (the microconch ) being male. This

12852-533: The most extreme and bizarre-looking example of a heteromorph is Nipponites , which appears to be a tangle of irregular whorls lacking any obvious symmetric coiling. Upon closer inspection, though, the shell proves to be a three-dimensional network of connected "U" shapes. Nipponites occurs in rocks of the upper part of the Cretaceous in Japan and the United States. Some ammonites have been found in association with

12978-557: The only species of mammal except for humans which exhibit exclusive homosexual behavior . About 10% of rams refuse to mate with ewes but readily mate with other rams, and thirty percent of all rams demonstrate at least some homosexual behavior. Additionally, a small number of females that were accompanied by a male fetus in utero (i.e. as fraternal twins ) are freemartins (female animals that are behaviorally masculine and lack functioning ovaries ). Sheep may fall victim to poisons, infectious diseases , and physical injuries. As

13104-472: The original shell, as well as the complete body chamber, still intact. Many Pierre Shale ammonites, and indeed many ammonites throughout earth history, are found inside concretions . Other fossils, such as many found in Madagascar and Alberta , Canada display iridescence . These iridescent ammonites are often of gem quality ( ammolite ) when polished. In no case would this iridescence have been visible during

13230-415: The plant that are easier to digest or higher in nutrition. Sheep, however, graze well in monoculture pastures where most goats fare poorly. Like all ruminants, sheep have a complex digestive system composed of four chambers, allowing them to break down cellulose from stems, leaves, and seed hulls into simpler carbohydrates . When sheep graze , vegetation is chewed into a mass called a bolus , which

13356-636: The position of other sheep in the flock. This constant monitoring is probably what keeps the sheep in a flock as they move along grazing. Sheep become stressed when isolated; this stress is reduced if they are provided with a mirror, indicating that the sight of other sheep reduces stress. Taste is the most important sense in sheep, establishing forage preferences, with sweet and sour plants being preferred and bitter plants being more commonly rejected. Touch and sight are also important in relation to specific plant characteristics, such as succulence and growth form. The ram uses his vomeronasal organ (sometimes called

13482-461: The preceding whorls, the specimen is said to be involute (e.g., Anahoplites ). Where it does not cover those preceding, the specimen is said to be evolute (e.g., Dactylioceras ). A thin living tube called a siphuncle passed through the septa, extending from the ammonite's body into the empty shell chambers. Through a hyperosmotic active transport process, the ammonite emptied water out of these shell chambers. This enabled it to control

13608-421: The productivity of flocks. Worms are the most common internal parasites. They are ingested during grazing, incubate within the sheep, and are expelled through the digestive system (beginning the cycle again). Oral anti-parasitic medicines, known as drenches , are given to a flock to treat worms, sometimes after worm eggs in the feces has been counted to assess infestation levels. Afterwards, sheep may be moved to

13734-403: The ram during courting; somewhat similar rumbling sounds may be made by the ewe, especially when with her neonate lambs. A snort (explosive exhalation through the nostrils) may signal aggression or a warning, and is often elicited from startled sheep. In sheep breeds lacking facial wool, the visual field is wide. In 10 sheep (Cambridge, Lleyn and Welsh Mountain breeds, which lack facial wool),

13860-418: The rim, results in the various suture patterns found. The septal curvature in nautiloids and ammonoids also differ in that the septa curves towards the opening in nautiloids, and away from the opening in ammоnoids. While nearly all nautiloids show gently curving sutures, the ammonoid suture line (the intersection of the septum with the outer shell) is variably folded, forming saddles ("peaks" that point towards

13986-466: The rock layer in which a particular species or genus is found to specific geologic time periods is often possible. Their fossil shells usually take the form of planispirals , although some helically spiraled and nonspiraled forms (known as heteromorphs ) have been found. The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams ' horns. Pliny

14112-425: The rumen, feed passes into the reticulum and the omasum ; special feeds such as grains may bypass the rumen altogether. After the first three chambers, food moves into the abomasum for final digestion before processing by the intestines . The abomasum is the only one of the four chambers analogous to the human stomach, and is sometimes called the "true stomach". Other than forage, the other staple feed for sheep

14238-469: The rump to prevent fly-strike, normally performed when the sheep is a lamb. Nose bots are fly larvae that inhabit a sheep's sinuses , causing breathing difficulties and discomfort. Common signs are a discharge from the nasal passage, sneezing, and frantic movement such as head shaking. External parasites may be controlled through the use of backliners , sprays or immersive sheep dips . A wide array of bacterial and viral diseases affect sheep. Diseases of

14364-494: The same rocks. However, because the dimorphic sizes are so consistently found together, they are more likely an example of sexual dimorphism within the same species. Whorl width in the body chamber of many groups of ammonites, as expressed by the width:diameter ratio, is another sign of dimorphism. This character has been used to separate "male" (Largiventer conch "L") from "female" (Leviventer conch "l"). The majority of ammonite species feature planispiral shells, tightly coiled in

14490-449: The same species or a group for which geographical and/or cultural separation from phenotypically similar groups has led to acceptance of its separate identity." Almost all sheep are classified as being best suited to furnishing a certain product: wool, meat, milk, hides, or a combination in a dual-purpose breed. Other features used when classifying sheep include face color (generally white or black), tail length, presence or lack of horns, and

14616-479: The sculpture of the inner and outer surfaces, but because they are so rarely found in position within the shell of the ammonite it is often unclear to which species of ammonite one kind of aptychus belongs. A number of aptychi have been given their own genus and even species names independent of their unknown owners' genus and species, pending future discovery of verified occurrences within ammonite shells. Although ammonites do occur in exceptional lagerstatten such as

14742-442: The sheep has 20 teeth. Mature sheep have 32 teeth. As with other ruminants, the front teeth in the lower jaw bite against a hard, toothless pad in the upper jaw. These are used to pick off vegetation, then the rear teeth grind it before it is swallowed. There are eight lower front teeth in ruminants, but there is some disagreement as to whether these are eight incisors , or six incisors and two incisor-shaped canines . This means that

14868-415: The shell is especially evident in the later ammonites of the Cretaceous. Ammonoids with a shell shape diverging from the typical planispiral form are known as heteromorphs , instead forming a conch with detached whorls (open coiling) or non-planispiral coiling. These types of shells evolved four times in ammonoids, with the first forms appearing already in the Devonian period. In late Norian age in Triassic

14994-548: The side of the shell. The lateral saddle and lobe are usually larger than the ventral saddle and lobe. Additional lobes developing towards the inner edge of a whorl are labelled umbilical lobes, which increase in number through ammonoid evolution as well as an individual ammonoid's development. In many cases the distinction between the lateral and umbilical regions are unclear; new umbilical features can develop from subdivisions of other umbilical features, or from subdivisions of lateral features. Lobes and saddles which are so far towards

15120-543: The siphuncle runs through the center of each chamber. However the very earliest nautiloids from the Late Cambrian and Ordovician typically had ventral siphuncles like ammonites, although often proportionally larger and more internally structured. The word "siphuncle" comes from the Neo-Latin siphunculus , meaning "little siphon". Originating from within the bactritoid nautiloids, the ammonoid cephalopods first appeared in

15246-575: The southern and central South American nations, and the British Isles are most closely associated with sheep production. There is a large lexicon of unique terms for sheep husbandry which vary considerably by region and dialect . Use of the word sheep began in Middle English as a derivation of the Old English word scēap . A group of sheep is called a flock. Many other specific terms for

15372-482: The various life stages of sheep exist, generally related to lambing, shearing, and age. As a key animal in the history of farming, sheep have a deeply entrenched place in human culture, and are represented in much modern language and symbolism . As livestock, sheep are most often associated with pastoral , Arcadian imagery. Sheep figure in many mythologies —such as the Golden Fleece —and major religions, especially

15498-411: The visual field ranged from 298° to 325°, averaging 313.1°, with binocular overlap ranging from 44.5° to 74°, averaging 61.7°. In some breeds, unshorn facial wool can limit the visual field; in some individuals, this may be enough to cause "wool blindness". In 60 Merinos, visual fields ranged from 219.1° to 303.0°, averaging 269.9°, and the binocular field ranged from 8.9° to 77.7°, averaging 47.5°; 36% of

15624-823: The way for invasive plants. However, sheep also prefer to eat invasives such as cheatgrass , leafy spurge , kudzu and spotted knapweed over native species such as sagebrush , making grazing sheep effective for conservation grazing . Research conducted in Imperial County, California compared lamb grazing with herbicides for weed control in seedling alfalfa fields. Three trials demonstrated that grazing lambs were just as effective as herbicides in controlling winter weeds. Entomologists also compared grazing lambs to insecticides for insect control in winter alfalfa. In this trial, lambs provided insect control as effectively as insecticides. Sheep are flock animals and strongly gregarious; much sheep behavior can be understood on

15750-423: Was confirmed in "visual cliff" experiments; behavioral responses indicating depth perception are seen in lambs at one day old. Sheep are thought to have colour vision, and can distinguish between a variety of colours: black, red, brown, green, yellow, and white. Sight is a vital part of sheep communication, and when grazing, they maintain visual contact with each other. Each sheep lifts its head upwards to check

15876-588: Was proposed in 1855 by Belgian geologist André Hubert Dumont and was accepted for the upper stage of the Upper Devonian by the Subcommission on Devonian Stratigraphy in 1981. It is named after Famenne , a natural region in southern Belgium. The lower GSSP, ratified in 1993, is located within the Coumiac Formation near Cessenon in southern France. Since 2017, the base of the Famennian has been defined by

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