36-572: The Proterocameroceratidae were the first of the Endocerida . They began early in the Ordovician with Proendoceras or similar genus which had developed endocones, replacing the diaphragms of the ellesmerocerid ancestor. Proterocameroceratids are long, straight or gently curved with a generally narrow siphuncle along the ventral margin. Septal necks are short, never quite reaching the previous septum and may vary in length ontogenically within
72-810: A superorder instead. Rousseau Flower rejected this separation on the grounds that endocerids were no more diverse or complex than any other order. He considered them to be simply another order within the Nautiloidea. Flower (1958) divided the Endocerida into two suborders, the Proterocamerocerina and the Endocerina. As he defined the two suborders, Proterocamerocerina included the Proterocameroceratidae , Manchuroceratidae , and Emmonsoceratidae , while Endocerina included
108-566: A 96.7% plant-based diet) and 2.57 (for Iceland , with 50% meat and fish, 50% plants). These values are comparable to those of non-apex predators such as the anchovy or pig . However, Peter D. Roopnarine criticized Bonhommeau's approach in 2014, arguing that humans are apex predators and that the HTL was based on terrestrial farming where indeed humans have a low trophic level, mainly eating producers (crop plants at level 1) or primary consumers (herbivores at level 2), which as expected places humans at
144-567: A complete picture. However, indirect evidence such as the absence of any discernible predator in an environment is suggestive. Anomalocaris was an aquatic apex predator, in the Cambrian. Its mouthparts are clearly predatory, and there were no larger animals in the seas at that time. Carnivorous theropod dinosaurs including Allosaurus and Tyrannosaurus are theorized to have been apex predators, based on their size, morphology, and dietary needs. A Permian shark, Triodus sessilis ,
180-693: A dozen cephalopod orders that appeared in the Lower Ordovician. They reached their greatest diversity during the Lower to Mid-Ordovician, but were already in decline by the middle of this period with most genera becoming extinct by the end of the Sandbian (late Ordovician), while some rare hangers on lasted into the Silurian . In any case, the endocerid lineage became completely extinct relatively early on in cephalopod history. Endocerids evolved from
216-628: A level slightly above 2. Roopnarine instead calculated the position of humans in two marine ecosystems, a Caribbean coral reef and the Benguela system near South Africa. In these systems, humans mainly eat predatory fish and have a fractional trophic level of 4.65 and 4.5, respectively, which in Roopnarine's view makes those humans apex predators. In 2021, Miki Ben-Dor and colleagues compared human biology to that of animals at various trophic levels. Using metrics as diverse as tool use and acidity of
252-531: A reduction in the population of sperm whales , apex predators with a fractional trophic level of 4.7, by hunting has caused an increase in the population of the large squid, with trophic level over 4 (carnivores that eat other carnivores). This effect, called mesopredator release , occurs in terrestrial and marine ecosystems; for instance, in North America, the ranges of all apex carnivores have contracted whereas those of 60% of mesopredators have grown in
288-714: A species. Connecting rings are thick and layered. Endocones are simple, especially in early forms but may be complex with secondary structures in later forms. The Proterocameroceratidae gave rise to the Piloceratidae early on, and later to the Manchuroceratidae and Chihlioceratidae, from which the Allotrioceratidae are derived, and later yet possibly to the Emmonsoceratidae and Najaceratidae. The Piloceratidae in turn may have given rise to
324-435: Is anecdotally reported to have reached lengths approaching 9 metres (30 ft), but these claims are problematic. The overwhelming majority of endocerids and nautiloids in general are much smaller, usually less than a meter long when fully grown. Endocerids had a relatively small body chamber as well as a proportionally large siphuncle , which in some genera reached nearly half the shell diameter. This suggests that much of
360-448: Is debated. Endocerids may have been the apex predators of the Ordovician, probably living close to the sea floor, and preying on trilobites , molluscs, brachiopods and other bottom-dwelling organisms. They were probably not active nektonic swimmers, but rather crawled over the floor of epicontinental seas or lay there in ambush. Although there is study that supports filter feeding ecology, according to hydrostatic properties, it
396-415: Is not likely and still supports benthic predators. Endocerids laid relatively large eggs, and hatched at a relatively large body size. It is likely that endocerids were demersal after hatching, as large eggs would make an easy target for predators in the pelagic zone. Endocerids may have migrated from their habitat in the open ocean to shallower water to lay their eggs. Endocerids were among some half
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#1732798338684432-827: Is shrinking the sea ice of the Arctic, forcing polar bears to fast on land for increasingly long periods. Dramatic changes in the Greater Yellowstone Ecosystem were recorded after the gray wolf , both an apex predator and a keystone species (one with a large effect on its ecosystem), was reintroduced to Yellowstone National Park in 1995 as a conservation measure. Elk , the wolves' primary prey, became less abundant and changed their behavior, freeing riparian zones from constant grazing and allowing willows , aspens , and cottonwoods to flourish, creating habitats for beaver , moose , and scores of other species. In addition to their effect on prey species,
468-473: The Cambrian period when animals such as Anomalocaris and Timorebestia dominated the seas. Humans have for many centuries interacted with other apex predators including the wolf , birds of prey , and cormorants to hunt game animals, birds, and fish respectively. More recently, humans have started interacting with apex predators in new ways. These include interactions via ecotourism , such as with
504-469: The Endoceratidae although a proterocameroceratid ancestor remains possible. Proterocameroceratids were probably mobile bottom predators that moved from place to place over the sea floor in search of prey or escape. Their shell was on one hand a carry over from some Cambrian monoplacophoran ancestor, passed on through previous orders, and on the other both a hydrodynamic facilitator and protection. But
540-676: The Piloceratidae and Endoceratidae . Endocerid classification since then has relied on a dichotomy between short-shelled forms with complex endocones and long-shelled forms with simple endocones. Endocerid relationships have been difficult to establish both within the order and relative to other nautiloids. Their generally orthoconic shell shape and dorsomyarian muscle scars are similar to the subclass Orthoceratoidea , which are ancestral to ammonoids (ammonites) and coleoids (squid, octopus, etc.). However, their nautilosiphonate connecting ring structure and lack of cameral deposits are more similar to living nautilus and their proposed ancestors,
576-476: The tiger shark , and through rewilding efforts, such as the proposed reintroduction of the Iberian lynx . Apex predators affect prey species' population dynamics and populations of other predators, both in aquatic and terrestrial ecosystems. Non-native predatory fish, for instance, have sometimes devastated formerly dominant predators. A lake manipulation study found that when the non-native smallmouth bass
612-659: The Lower Paleozoic with cone-like deposits in their siphuncle . Endocerida was a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Silurian . Their shells were variable in form. Some were straight ( orthoconic ), others curved (cyrtoconic); some were long (longiconic), others short (breviconic). Some long-shelled forms like Endoceras attained shell lengths close to 6 metres (20 ft). The related Cameroceras
648-489: The Orthocerida and Actinocerida . Endocerids reached enormous body sizes. The largest confirmed specimen, belonging to Endoceras giganteum , is 3 metres (9.8 ft) long as preserved, but is missing a substantial portion of its aboral end. The reconstructed length of the shell is nearly 6 metres (20 ft). An alleged endocerid specimen 30 feet (9.1 m) long is unconfirmed. The mode of life of endocerids
684-596: The consequences of both controlling prey density and restricting smaller predators, and may be capable of self-regulation. They are central to the functioning of ecosystems, the regulation of disease, and the maintenance of biodiversity. When introduced to subarctic islands, for example, Arctic foxes ' predation of seabirds has been shown to turn grassland into the tundra . Such wide-ranging effects on lower levels of an ecosystem are termed trophic cascades . The removal of top-level predators, often through human agency, can cause or disrupt trophic cascades. For example,
720-548: The counties of Norfolk , Cumbria , and Northumberland in England, and Aberdeenshire in Scotland as part of the rewilding movement. The reintroduction of large predators is controversial, in part because of concern among farmers for their livestock . Conservationists such as Paul Lister propose instead to allow wolves and bears to hunt their prey in a "managed environment" on large fenced reserves; however, this undermines
756-474: The earlier ellesmerocerids , most likely from a genus similar to Pachendoceras . This ellesmerocerid gave rise to Proendoceras , the earliest representative of the Proterocameroceratidae and hence of the Endocerida. Endocerids evolved from ellesmerocerids by reduction of siphuncle diaphragms and the development of endocones. In the early part of the mid-Lower Ordovician, the Endocerida quickly diversified into many different families. In true endocerids, there
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#1732798338684792-971: The form of wolves, and in turn with domestic dogs , for 40,000 years; this collaboration may have helped modern humans to outcompete the Neanderthals . Humans still hunt with dogs , which have often been bred as gun dogs to point to , flush out , or retrieve prey . The Portuguese Water Dog was used to drive fish into nets. Several breeds of dog have been used to chase large prey such as deer and wolves. Eagles and falcons , which are apex predators, are used in falconry , hunting birds or mammals. Tethered cormorants , also top predators, have been used to catch fish . Ecotourism sometimes relies on apex predators to attract business. Tour operators may in consequence decide to intervene in ecosystems, for example by providing food to attract predators to areas that can conveniently be visited. This in turn can have effects on predator population and therefore on
828-426: The front of the shell. The Proterocameroceratidae ultimately suffered the extinction at the end of the Ordovician, but not before having given rise to a variety of endocerid families. They remain a subject of interesting research. Endocerida † Cyrtendoceratidae † Endoceratidae † Proterocameroceratidae † Yorkoceratidae Endocerida is an extinct nautiloid order, a group of cephalopods from
864-403: The highest trophic levels . Food chains are often far shorter on land, usually limited to being secondary consumers – for example, wolves prey mostly upon large herbivores (primary consumers), which eat plants (primary producers). The apex predator concept is applied in wildlife management , conservation , and ecotourism . Apex predators have a long evolutionary history, dating at least to
900-500: The numerous piloceratid-like families were placed within a new order, Bisonocerida . Bisonocerida may still be related to endocerids within Endoceratoidea. Apex predator An apex predator , also known as a top predator or superpredator , is a predator at the top of a food chain , without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics , meaning that they occupy
936-496: The park. Ecologists have debated whether humans are apex predators. For instance, Sylvain Bonhommeau and colleagues argued in 2013 that across the global food web, a fractional human trophic level (HTL) can be calculated as the mean trophic level of every species in the human diet, weighted by the proportion that that species forms in the diet. This analysis gives an average HTL of 2.21, varying between 2.04 (for Burundi , with
972-466: The past two centuries. Because apex predators have powerful effects on other predators, herbivores, and plants, they can be important in nature conservation. Humans have hunted many apex predators close to extinction, but in some parts of the world, these predators are now returning. They are increasingly threatened by climate change . For example, the polar bear requires extensive areas of sea ice to hunt its prey, typically seals, but climate change
1008-413: The shells of nautiloids, such as the proterocameroceratids was also an impediment to true squidlike or fishlike swimming. They could not have had fins for propulsion or steering, only the hyponome for spontaneous jet mobility and their tentacles by which to crawl across the sea floor and to grasp at things. The diagnostic endocones in the early part of the siphuncle balanced the weight of the animal living at
1044-507: The stomach, they concluded that humans evolved as apex predators, diversifying their diets in response to the disappearance of most of the megafauna that had once been their primary source of food. Apex predators are thought to have existed since at least the Cambrian period, around 500 million years ago. Extinct species cannot be directly determined to be apex predators as their behavior cannot be observed, and clues to ecological relationships, such as bite marks on bones or shells, do not form
1080-412: The subclass Multiceratoidea . Some studies have re-established Endoceratoidea to clarify that endocerids occupy a unique subclass of nautiloids. Restudy of piloceratid-like families with complex endocones has suggested that Endocerida in its broadest form is polyphyletic , with piloceratid-like and proterocameroceratid-like members having independent origins from ellesmerocerids. In light of this issue,
1116-495: The visceral mass may have been housed within the siphuncle itself rather than just in the body chamber as with other nautiloids (Teichert, 1964). Endocerids are primarily distinguished by the presence of conical calcareous deposits, known as endocones, found in the more apical portion of the siphuncle. They are thought to act as a counterweight for the animal’s body. The chambers ( camerae ) of endocerids are always free of organic deposits, unlike orthoceratoid cephalopod orders such as
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1152-576: The wider ecosystem. As a result, provisioning of species such as the tiger shark is controversial, but its effects are not well established by empirical evidence. Other affected apex predators include big cats and crocodiles. In some densely populated areas like the British Isles , all the large native predators like the wolf, bear, wolverine and lynx have become extirpated , allowing herbivores such as deer to multiply unchecked except by hunting. In 2015, plans were made to reintroduce lynx to
1188-562: The wolves' presence also affected one of the park's vulnerable species , the grizzly bear : emerging from hibernation , having fasted for months, the bears chose to scavenge wolf kills, especially during the autumn as they prepared to hibernate once again. The grizzly bear gives birth during hibernation, so the increased food supply is expected to produce an increase in the number of cubs observed. Dozens of other species, including eagles, ravens, magpies , coyotes, and black bears have also been documented as scavenging from wolf kills within
1224-521: Was a trend of overall increasing size, eventually resulting in massive orthoconic genera such as Endoceras and Cameroceras . In another lineage (now known as Bisonocerida ), the siphuncle grew more complex, resulting in genera such as Chihlioceras and Allotrioceras . Citing its diversity, Curt Teichert (1964) placed the Endocerida in its own subclass called the Endoceroidea or Endoceratoidea (which some Russian paleontologists ranked as
1260-457: Was discovered containing two amphibians ( Archegosaurus decheni and Cheliderpeton latirostre ), one of which had consumed a fish, Acanthodes bronni , showing that the shark had lived at a trophic level of at least 4. Among more recent fossils, the saber-tooth cats, like Smilodon , are considered to have been apex predators in the Cenozoic . Humans hunted with apex predators in
1296-647: Was removed, lake trout , the suppressed native apex predator, diversified its prey selection and increased its trophic level . As a terrestrial example, the badger , an apex predator, preys upon and also competes with the hedgehog , a mesopredator , for food such as insects, small mammals, reptiles, amphibians, and the eggs of ground-nesting birds. Removal of badgers (in a trial investigating bovine tuberculosis ) caused hedgehog densities to more than double. Predators that exert top-down control on organisms in their community are often considered keystone species . Apex predators can have profound effects on ecosystems, as
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