Poaceae or Gramineae is a large and nearly ubiquitous family of monocotyledonous flowering plants known as grasses referred to collectively as grass. Poaceae includes the cereal grasses and the grasses of natural grassland and cultivated lawns and pasture. Grasses have stems that are hollow except at the nodes and narrow alternate leaves borne in two ranks; the lower part of each leaf encloses the stem. With around 780 genera and around 12,000 species, Poaceae are the fifth-largest plant family, following the Asteraceae, Orchidaceae and Rubiaceae. Grasslands such as savannah and prairie where grasses are dominant are estimated to constitute 40.5% of the land area of the Earth, excluding Greenland and Antarctica. Grasses are an important part of the vegetation in many other habitats, including wetlands and tundra; the Poaceae are the most economically important plant family, providing staple foods from domesticated cereal crops such as maize, rice and millet as well as forage, building materials and fuel.
Though they are called "grasses", seagrasses and sedges fall outside this family. The rushes and sedges are related to the Poaceae, being members of the order Poales, but the seagrasses are members of order Alismatales; the name Poaceae was given by John Hendley Barnhart in 1895, based on the tribe Poeae described in 1814 by Robert Brown, the type genus Poa described in 1753 by Carl Linnaeus. The term is derived from the Ancient Greek πόα. Grasses include some of the most versatile plant life-forms, they became widespread toward the end of the Cretaceous period, fossilized dinosaur dung have been found containing phytoliths of a variety that include grasses that are related to modern rice and bamboo. Grasses have adapted to conditions in lush rain forests, dry deserts, cold mountains and intertidal habitats, are the most widespread plant type. A cladogram shows subfamilies and approximate species numbers in brackets: Before 2005, fossil findings indicated that grasses evolved around 55 million years ago.
Recent findings of grass-like phytoliths in Cretaceous dinosaur coprolites have pushed this date back to 66 million years ago. In 2011, revised dating of the origins of the rice tribe Oryzeae suggested a date as early as 107 to 129 Mya. Wu, You & Li described grass microfossils extracted from a specimen of the hadrosauroid dinosaur Equijubus normani from the Early Cretaceous Zhonggou Formation; the authors noted that India became separated from Antarctica, therefore all other continents at the beginning of late Aptian, so the presence of grasses in both India and China during the Cretaceous indicates that the ancestor of Indian grasses must have existed before late Aptian. Wu, You & Li considered the Barremian origin for grasses to be probableThe relationships among the three subfamilies Bambusoideae and Pooideae in the BOP clade have been resolved: Bambusoideae and Pooideae are more related to each other than to Oryzoideae; this separation occurred within the short time span of about 4 million years.
According to Lester Charles King the spread of grasses in the Late Cenozoic would have changed patterns of hillslope evolution favouring slopes that are convex upslope and concave downslope and lacking a free face were common. King argued that this was the result of more acting surface wash caused by carpets of grass which in turn would have resulted in more soil creep. Grasses may be annual or perennial herbs with the following characteristics: The stems of grasses, called culms, are cylindrical and are hollow, plugged at the nodes, where the leaves are attached. Grass leaves are nearly always alternate and distichous, have parallel veins; each leaf is differentiated into a lower sheath hugging a blade with entire margins. The leaf blades of many grasses are hardened with silica phytoliths, which discourage grazing animals. A membranous appendage or fringe of hairs called the ligule lies at the junction between sheath and blade, preventing water or insects from penetrating into the sheath. Flowers of Poaceae are characteristically arranged in each having one or more florets.
The spikelets are further grouped into spikes. The part of the spikelet that bears the florets is called the rachilla. A spikelet consists of two bracts at called glumes, followed by one or more florets. A floret consists of the flower surrounded by two bracts, one external—the lemma—and one internal—the palea; the flowers are hermaphroditic—maize being an important exception—and anemophilous or wind-pollinated, although insects play a role. The perianth is reduced to two scales, called lodicules, that expand and contract to spread the lemma and palea; this complex structure can be seen in the image on the right. The fruit of grasses is a caryopsis. A tiller is a leafy shoot other than the first shoot produced from the seed. Grass blades grow at the base of the blade and not from elongated stem tips; this low growth point evolved in response to grazing animals and allows grasses to be grazed or mown without severe damage to the plant. Three general classifications of growth habit present in g
Andrewsarchus is an extinct genus of mammal that lived during the middle Eocene epoch in what is now Inner Mongolia, China. Only one species is recognized, A. mongoliensis, known from a single skull of great size discovered in 1923 during the expeditions to central Asia by the American Museum of Natural History. Classified as a mesonychid since its original description, most recent studies classify it as an artiodactyl, in one study as a member of the clade Cetancodontamorpha related to entelodonts and whales; the only known skull was found at a locality in the lower levels of the middle Eocene Irdin Manha Formation of Inner Mongolia, by the paleontological assistant Kan Chuen Pao during the spring of the second year of the Central Asiatic Expeditions of the AMNH, led by the explorer and naturalist Roy Chapman Andrews. The skull is now on display at the American Museum of Natural History in New York; the genus name was dedicated to Roy Chapman Andrews by Osborn and it derives from the surname "Andrews" + Greek: ἀρχός, "leader", "chief" or "commander".
The species epithet mongoliensis refers to the region where the type material was found, Inner Mongolia. It was classified in the clade Mesonychia due to the similarity in structure between its teeth and skull with those of other mesonychid species known from complete skeletons, much of this was based only on Osborn's original publication, more recent studies have found it to have no special mesonychid affinities, instead grouping it with various artiodactyl clades. Indeed, one study has not only found them to be closer to entelodonts, but as kin to Whippomorpha in the clade Cetacodontamorpha. Osborn declared Andrewsarchus as the largest terrestrial mammalian carnivore known on the basis of the length of the skull, which he used to estimate its size comparing it to the mesonychid Mesonyx. However, since the known morphology of Andrewsarchus is entelodont-like and very different to mesonychids in habits and in body proportions, according to Szalay and Gould if a size estimate has to be made it would be more appropriate to follow the proportions of entelodonts.
The type skull of Andrewsarchus mongoliensis is 83.4 cm in basal length, with a long snout comprising 60% of that measurement. The orbits of the eyes are set low and separated from one another by the snout. Andrewsarchus mongoliensis has a complete placental tooth formula with 3 incisors, 1 canine, 4 premolars and 3 molars in each side of the jaws, like in entelodonts the incisors are arranged in a semicircular configuration, the second and third premolars are elongated and single cusped, the crowns of the molars are wrinkled and the first and second molars are much more worn than the precedent and subsequent teeth, in fact, the molars are so alike to those of entelodonts that it has been suggested that had they been found in isolation they would have been assigned to entelodonts. Between the dental features unique to A. mongoliensis we find enlarged second incisors, as big as the canines, which despite not being preserved can be estimated from the diameter of their tooth sockets, they were proportionally small compared to the whole dentition and the size of the skull according to Szalay and Gould contra Osborn
The Holocene is the current geological epoch. It began 11,650 cal years before present, after the last glacial period, which concluded with the Holocene glacial retreat; the Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1, it is considered by some to be an interglacial period within the Pleistocene Epoch. The Holocene has seen the growth and impacts of the human species worldwide, including all its written history, development of major civilizations, overall significant transition toward urban living in the present. Human impacts on modern-era Earth and its ecosystems may be considered of global significance for future evolution of living species, including synchronous lithospheric evidence, or more hydrospheric and atmospheric evidence of human impacts. In July 2018, the International Union of Geological Sciences split the Holocene epoch into three distinct subsections, Greenlandian and Meghalayan, as proposed by International Commission on Stratigraphy.
The boundary stratotype of Meghalayan is a speleothem in Mawmluh cave in India, the global auxiliary stratotype is an ice core from Mount Logan in Canada. The name Holocene comes from the Ancient Greek words ὅλος and καινός, meaning "entirely recent", it is accepted by the International Commission on Stratigraphy that the Holocene started 11,650 cal years BP. The Subcommission on Quaternary Stratigraphy quotes Gibbard and van Kolfschoten in Gradstein Ogg and Smith in stating the term'Recent' as an alternative to Holocene is invalid and should not be used and observe that the term Flandrian, derived from marine transgression sediments on the Flanders coast of Belgium has been used as a synonym for Holocene by authors who consider the last 10,000 years should have the same stage-status as previous interglacial events and thus be included in the Pleistocene; the International Commission on Stratigraphy, considers the Holocene an epoch following the Pleistocene and the last glacial period. Local names for the last glacial period include the Wisconsinan in North America, the Weichselian in Europe, the Devensian in Britain, the Llanquihue in Chile and the Otiran in New Zealand.
The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations: Preboreal, Atlantic and Subatlantic. Note: "ka" means "kilo-annum" Before Present, i.e. 1,000 years before 1950 The Blytt–Sernander classification of climatic periods defined by plant remains in peat mosses, is being explored. Geologists working in different regions are studying sea levels, peat bogs and ice core samples by a variety of methods, with a view toward further verifying and refining the Blytt–Sernander sequence, they find a general correspondence across Eurasia and North America, though the method was once thought to be of no interest. The scheme was defined for Northern Europe, but the climate changes were claimed to occur more widely; the periods of the scheme include a few of the final pre-Holocene oscillations of the last glacial period and classify climates of more recent prehistory. Paleontologists have not defined any faunal stages for the Holocene. If subdivision is necessary, periods of human technological development, such as the Mesolithic and Bronze Age, are used.
However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world. Climatically, the Holocene may be divided evenly into the Neoglacial periods. According to some scholars, a third division, the Anthropocene, has now begun; the International Commission on Stratigraphy Subcommission on Quaternary Stratigraphy’s working group on the'Anthropocene' note this term is used to denote the present time interval in which many geologically significant conditions and processes have been profoundly altered by human activities. The'Anthropocene' is not a formally defined geological unit. Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years. However, ice melt caused world sea levels to rise about 35 m in the early part of the Holocene. In addition, many areas above about 40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 m due to post-glacial rebound over the late Pleistocene and Holocene, are still rising today.
The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea. Holocene marine fossils are known, from Vermont and Michigan. Other than higher-latitude temporary marine incursions associated with glacial depression, Holocene fossils are found in lakebed and cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any tectonic uplift of non-glacial origin. Post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea; the region continues to rise, still causing weak earthquakes across Northern Europe. The equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries. Climate has been stable over the Holocene. Ice core
Paleocene–Eocene Thermal Maximum
The Paleocene–Eocene Thermal Maximum, alternatively "Eocene thermal maximum 1", known as the "Initial Eocene" or "Late Paleocene Thermal Maximum", was a time period with more than 8 °C warmer global average temperature than today. This climate event began at the time boundary of the Paleogene, between the Paleocene and Eocene geological epochs; the exact age and duration of the event is uncertain but it is estimated to have occurred around 55.5 million years ago. The associated period of massive carbon injection into the atmosphere has been estimated to have lasted no longer than 20,000 years; the entire warm period lasted for about 200,000 years. Global temperatures increased by 5–8 °C; the carbon dioxide was released in two pulses, the first lasting less than 2,000 years. Such a repeated carbon release is in line with current global warming. A main difference is that during the Paleocene–Eocene Thermal Maximum, the planet was ice-free. However, the amount of released carbon, according to a recent study, suggests a modest 0.2 gigatonnes per year.
The onset of the Paleocene–Eocene Thermal Maximum has been linked to an initial 5 °C temperature rise and to extreme changes in Earth's carbon cycle. The period is marked by a prominent negative excursion in carbon stable isotope records from around the globe. Stratigraphic sections of rock from this period reveal numerous other changes. Fossil records for many organisms show major turnovers. For example, in the marine realm, a mass extinction of benthic foraminifera, a global expansion of subtropical dinoflagellates, an appearance of excursion, planktic foraminifera and calcareous nanofossils all occurred during the beginning stages of PETM. On land, modern mammal orders appear in Europe and in North America. Sediment deposition changed at many outcrops and in many drill cores spanning this time interval. At least since 1997, the Paleocene–Eocene Thermal Maximum has become a focal point of considerable geoscience research because it provides the best past analog by which to understand impacts of global climate warming and of massive carbon input to the ocean and atmosphere, including ocean acidification.
Although it is now accepted that the PETM represents a "case study" for global warming and massive carbon input to Earth's surface, the cause and overall significance of the event remain perplexing. The configuration of oceans and continents was somewhat different during the early Paleogene relative to the present day; the Panama Isthmus did not yet connect North America and South America, this allowed direct low-latitude circulation between the Pacific and Atlantic Oceans. The Drake Passage, which now separates South America and Antarctica, was closed, this prevented thermal isolation of Antarctica; the Arctic was more restricted. Although various proxies for past atmospheric CO2 levels in the Eocene do not agree in absolute terms, all suggest that levels were much higher than at present. In any case, there were no significant ice sheets during this time. Earth surface temperatures increased by about 6 °C from the late Paleocene through the early Eocene, culminating in the "Early Eocene Climatic Optimum".
Superimposed on this long-term, gradual warming were at least two "hyperthermals". These can be defined as geologically brief events characterized by rapid global warming, major changes in the environment, massive carbon addition. Of these, the PETM was the most extreme and the first. Another hyperthermal occurred at 53.7 Ma, is now called ETM-2. However, additional hyperthermals occurred at about 53.6 Ma, 53.3, 53.2 and 52.8 Ma. The number, absolute ages, relative global impact of the Eocene hyperthermals are the source of considerable current research. Whether they only occurred during the long-term warming, whether they are causally related to similar events in older intervals of the geological record are open issues. Acidification of deep waters, the spreading from the North Atlantic can explain spatial variations in carbonate dissolution. Model simulations show acidic water accumulation in the deep North Atlantic at the onset of the event. At the start of the PETM, average global temperatures increased by 6 °C within about 20,000 years.
This warming was superimposed on "long-term" early Paleogene warming, is based on several lines of evidence. There is a prominent negative excursion in the δ18O of foraminifera shells, both those made in surface and deep ocean water; because there was a paucity of continental ice in the early Paleogene, the shift in δ18O probably signifies a rise in ocean temperature. The temperature rise is supported by analyses of fossil assemblages, the Mg/Ca ratios of foraminifera, the ratios of certain organic compounds, such as TEX86. Precise limits on the global temperature rise during the PETM and whether this varied with latitude remain open issues. Oxygen isotope and Mg/Ca of carbonate shells precipitated in surface waters of the ocean are used measurements for reconstructing past temperature. On the other hand and other tem
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Kelp grows in "underwater forests" in shallow oceans, is thought to have appeared in the Miocene, 23 to 5 million years ago; the organisms require nutrient-rich water with temperatures between 6 and 14 °C. They are known for their high growth rate—the genera Macrocystis and Nereocystis can grow as fast as half a metre a day reaching 30 to 80 metres. Through the 19th century, the word "kelp" was associated with seaweeds that could be burned to obtain soda ash; the seaweeds used included species from both the orders Fucales. The word "kelp" was used directly to refer to these processed ashes. In most kelp, the thallus consists of leaf-like structures known as blades. Blades originate from the stipes; the holdfast, a root-like structure, anchors the kelp to the substrate of the ocean. Gas-filled bladders form at the base of blades of American species, such as Nereocystis lueteana, to hold the kelp blades close to the surface.
Growth occurs at the base of the meristem. Growth may be limited by grazing. Sea urchins, for example, can reduce entire areas to urchin barrens; the kelp life cycle involves a diploid haploid gametophyte stage. The haploid phase begins when the mature organism releases many spores, which germinate to become male or female gametophytes. Sexual reproduction results in the beginning of the diploid sporophyte stage, which will develop into a mature individual; the parenchymatous thalli are covered with a mucilage layer, rather than cuticle. Kelp may develop dense forests with high production and ecological function. Along the Norwegian coast these forests cover 5800 km2, they support large numbers of animals. Numerous sessile animals are found on kelp stipes and mobile invertebrate fauna are found in high densities on epiphytic algae on the kelp stipes and on kelp holdfasts. More than 100,000 mobile invertebrates per square meter are found on kelp stipes and holdfasts in well-developed kelp forests.
While larger invertebrates and in particular sea urchins Strongylocentrotus droebachiensis are important secondary consumers controlling large barren ground areas on the Norwegian coast, they are scarce inside dense kelp forests. Giant kelp can be harvested easily because of its surface canopy and growth habit of staying in deeper water. Kelp ash is rich in alkali. In great amount, kelp ash can be used in glass production; until the Leblanc process was commercialized in the early 19th century, burning of kelp in Scotland was one of the principal industrial sources of soda ash. Alginate, a kelp-derived carbohydrate, is used to thicken products such as ice cream, salad dressing, toothpaste, as well as an ingredient in exotic dog food and in manufactured goods. Alginate powder is used in general dentistry and orthodontics for making impressions of the upper and lower arches. Kombu, several Pacific species of kelp, is a important ingredient in Chinese and Korean cuisines. Kombu is used to flavor broths and stews, as a savory garnish for rice and other dishes, as a vegetable, a primary ingredient in popular snacks.
Transparent sheets of kelp are used as an edible decorative wrapping for rice and other foods. Kombu can be used to soften beans during cooking, to help convert indigestible sugars and thus reduce flatulence; because of its high concentration of iodine, brown kelp has been used to treat goiter, an enlargement of the thyroid gland caused by a lack of iodine, since medieval times. In 2010, researchers found that alginate, the soluble fibre substance in sea kelp, was better at preventing fat absorption than most over-the-counter slimming treatments in laboratory trials; as a food additive, it may be used to reduce fat absorption and thus obesity. Kelp in its natural form has not yet been demonstrated to have such effects. Commercial production of kelp harvested from its natural habitat has taken place in Japan for over a century. Many countries today consume laminaria products. Laminaria japonica, the important commercial seaweed, was first introduced into China in the late 1920s from Hokkaido, Japan.
Yet mariculture of this alga on a large commercial scale was realized in China only in the 1950s. Between the 1950s and the 1980s, kelp production in China increased from about 60 to over 250,000 dry weight metric tons annually. Kelp has a high rate of growth and its decay is quite efficient in yielding methane, as well as sugars that can be converted to ethanol, it has been proposed. Unlike some biofuels such as corn ethanol, kelp energy avoids "food vs fuel" issues and does not require freshwater irrigation; some of the earliest evidence for human use of marine resources, coming from Middle Stone Age sites in South Africa, includes the harvesting of foods such as abalones and mussels associated with kelp forest habitats. In 2007, Erlandson et al. suggested that kelp forests around the Pacific Rim may have facilitated the dispersal of anatomically modern humans following a coastal route from Northeast Asia to the Americas. This "kelp highway hypothesis" suggested that productive kelp forests supported rich and dive
Mammals are vertebrate animals constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding their young, a neocortex, fur or hair, three middle ear bones. These characteristics distinguish them from reptiles and birds, from which they diverged in the late Triassic, 201–227 million years ago. There are around 5,450 species of mammals; the largest orders are the rodents and Soricomorpha. The next three are the Primates, the Cetartiodactyla, the Carnivora. In cladistics, which reflect evolution, mammals are classified as endothermic amniotes, they are the only living Synapsida. The early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period around 300 million years ago, this group diverged from the sauropsid line that led to today's reptiles and birds; the line following the stem group Sphenacodontia split off several diverse groups of non-mammalian synapsids—sometimes referred to as mammal-like reptiles—before giving rise to the proto-mammals in the early Mesozoic era.
The modern mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, have been among the dominant terrestrial animal groups from 66 million years ago to the present. The basic body type is quadruped, most mammals use their four extremities for terrestrial locomotion. Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale—the largest animal on the planet. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. All modern mammals give birth to live young, except the five species of monotremes, which are egg-laying mammals; the most species-rich group of mammals, the cohort called placentals, have a placenta, which enables the feeding of the fetus during gestation. Most mammals are intelligent, with some possessing large brains, self-awareness, tool use. Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals and echolocation.
Mammals can organize themselves into fission-fusion societies and hierarchies—but can be solitary and territorial. Most mammals are polygynous. Domestication of many types of mammals by humans played a major role in the Neolithic revolution, resulted in farming replacing hunting and gathering as the primary source of food for humans; this led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, the development of the first civilizations. Domesticated mammals provided, continue to provide, power for transport and agriculture, as well as food and leather. Mammals are hunted and raced for sport, are used as model organisms in science. Mammals have been depicted in art since Palaeolithic times, appear in literature, film and religion. Decline in numbers and extinction of many mammals is driven by human poaching and habitat destruction deforestation. Mammal classification has been through several iterations since Carl Linnaeus defined the class.
No classification system is universally accepted. George Gaylord Simpson's "Principles of Classification and a Classification of Mammals" provides systematics of mammal origins and relationships that were universally taught until the end of the 20th century. Since Simpson's classification, the paleontological record has been recalibrated, the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself through the new concept of cladistics. Though field work made Simpson's classification outdated, it remains the closest thing to an official classification of mammals. Most mammals, including the six most species-rich orders, belong to the placental group; the three largest orders in numbers of species are Rodentia: mice, porcupines, beavers and other gnawing mammals. The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apes and lemurs. According to Mammal Species of the World, 5,416 species were identified in 2006.
These were grouped into 153 families and 29 orders. In 2008, the International Union for Conservation of Nature completed a five-year Global Mammal Assessment for its IUCN Red List, which counted 5,488 species. According to a research published in the Journal of Mammalogy in 2018, the number of recognized mammal species is 6,495 species included 96 extinct; the word "mammal" is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from the Latin mamma. In an influential 1988 paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes and therian m
Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were the largest species of apex predators in South America during the Cenozoic era. They ranged in height from 1–3 m tall, their closest modern-day relatives are believed to be the 80-centimetre-tall seriemas. Titanis walleri, one of the larger species, is known from Florida in North America; this makes the phorusrhacids the only known large South American predator to migrate north in the Great American Interchange that followed the formation of the Isthmus of Panama land bridge. It was once believed that T. walleri became extinct in North America around the time of the arrival of humans, but subsequent datings of Titanis fossils provided no evidence for their survival after 1.8 Ma. However, reports from Uruguay of new findings of small forms dating to 18,000 and 96,000 years ago would imply that phorusrhacids survived there until recently. Phorusrhacids may have made their way into Africa.
A possible European form, has been identified, suggesting that this group had a wider geographical range in the Paleogene. The related bathornithids occupied a similar ecological niche in North America across the Eocene to Early Miocene. At least one analysis recovers Bathornis as sister taxa to phorusrhacids, on the basis of shared features in the jaws and coracoid, though this has been contested, as these might have evolved independently for the same carnivorous, flightless lifestyle. Based on Claudia P. Tambussi, Ricardo de Mendoza, Federico J. Degrange, Mariana B. Picasso's work, the phorusrhacid's neck can be divided into three main regions. In the higher regions of the neck, the phorusrhacid has bifurcate neural spines, while it has high neural spines in its lower regions; this suggests that the phorusrhacid had a flexible and developed neck allowing it to carry its heavy head and strike with terrifying speed and power. Although the phorusrhacid externally looks like it has a short neck, its flexible skeletal neck structure proves that it could expand farther beyond the expected reach and intimidate its prey using its height, allowing it to strike more easily.
Once stretched out into its full length in preparation for a downward strike, its developed neck muscles and heavy head could produce enough momentum and power to cause fatal damage to the terror bird's prey. Kelenken guillermoi, from the Langhian stage of the Miocene epoch, some 15 million years ago, discovered in the Collón Curá Formation in Patagonia in 2006, represents the largest bird skull yet found; the fossil has been described as being a 71-centimetre, nearly intact skull. The beak is 46 cm long and curves in a hook shape that resembles an eagle's beak. Most species described as phorusrhacid birds were smaller, 60–90 cm tall, but the new fossil belongs to a bird that stood about 3 m tall. Scientists theorize that the large terror birds were nimble and quick runners, able to reach speeds of 48 km/h. Examination of phorusrhacid habitats indicates that phorusrhacids may have presented intense competition to predatory marsupial sparassodonts such as borhyaenids and thylacosmilids, causing the mammalian predators to choose forested habitats to avoid the more successful and aggressive avian predators on the open plains.
Most phorusrhacids were fast runners. All members possessed a powerful neck and sharp talons; however with these attributes, the phorusrhacids are assumed to have preyed on small animals that could be dispatched with a minimum of struggle. This is due to the fact that with the phorusrhacids' beak proportions, the jaw could not generate a great deal of bite force with which to kill the prey; this is disputable as many big-game hunting predators such as Smilodon, great white sharks and Allosaurus have weaker bite forces and laterally weak skulls as adaptations towards, not away from, killing large prey, relying instead on the presence of a cutting edge, a wide gape made possible by the reduction of jaw musculature, the driving force of the body or neck. Since phorusrhacids share many of the same adaptations, such as a large, laterally flattened skull with a sharp-edged beak and powerful neck musculature, it is possible that they were specialized predators of large prey; the bones of the beak were fused together, making the beak more resilient to force from the front to back direction, thus suggesting that it could cause a great amount of harm through pecking as opposed to side-to-side head movements like shaking prey.
Speaking, it is thought that a terror bird would use its feet to injure prey by kicking it, to hold the prey down and dispatch by pecking at it with its large beak. Larger prey may have been attacked by pecking and kicking, or by using the beak as a blade to strike at or slash vital organs, it has been shown that at least some phorusrhacids like Andalgalornis, while fast runners in a straight line, were poor at tight turns at speed, which contradicts the idea of phorusrhacids being agile predators of small prey. All phorusrhacids are thought to have been carnivorous; the strong downwards curve from the