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02.12 03:18 - Encyclopedia Largest prehistoric animals Vol.6 Insects part1 Meganisoptera, Palaeodictyoptera, Hymenoptera,Siphonaptera
Автор: valentint Категория: Забавление   
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Insects (Insecta)
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Insects are the most evolutionarily successful group of organisms in the 4-billion-year history of life on earth, with perhaps 5 million species alive today and untold millions of extinct species. Although fossils of insects are not as abundant as has been found for some other types of organisms, the insect fossil record extends back for 400 million years, making them among the oldest terrestrial animals known, and the fossils contribute unique insight into the evolutionary history of insects. Particularly significant periods in the evolution of insects are the Paleozoic, Triassic, and Cretaceous. Key features that gave rise to their spectacular success, notably flight and complete metamorphosis, originated at least 300 and 250 million years ago (mya), respectively.The evolutionary relationship of insects to other animal groups remains unclear.
The higher-level
phylogeny of the arthropods continues to be a matter of debate and research. In 2008, researchers at Tufts University uncovered what they believe is the world"s oldest known full-body impression of a primitive flying insect,a 300-million-year-old specimen from the Carboniferous period.The oldest definitive insect fossil is the Devonian Rhyniognatha hirsti, from the 396-million-year-old Rhynie chert. It may have superficially resembled a modern-day silverfish insect. This species already possessed dicondylic mandibles (two articulations in the mandible), a feature associated with winged insects, suggesting that wings may already have evolved at this time. Thus, the first insects probably appeared earlier, in the Silurian period.
Four super radiations of insects have occurred: beetles (evolved about 300 million years ago), flies (evolved about 250 million years ago), and moths and wasps (evolved about 150 million years ago). These four groups account for the majority of described species. The flies and moths along with the fleas evolved from the Mecoptera.
The origins of insect flight remain obscure, since the earliest winged insects currently known appear to have been capable fliers. Some extinct insects had an additional pair of winglets attaching to the first segment of the thorax, for a total of three pairs. As of 2009, no evidence suggests the insects were a particularly successful group of animals before they evolved to have wings.
Late Carboniferous and Early Permian insect orders include both extant groups, their stem groups,and a number of Paleozoic groups, now extinct. During this era, some giant dragonfly-like forms reached wingspans of 55 to 70 cm (22 to 28 in), making them far larger than any living insect. This gigantism may have been due to higher atmospheric oxygen levels that allowed increased respiratory efficiency relative to today. The lack of flying vertebrates could have been another factor. Most extinct orders of insects developed during the Permian period that began around 270 million years ago. Many of the early groups became extinct during the Permian-Triassic extinction event, the largest mass extinction in the history of the Earth, around 252 million years ago.
The remarkably successful
Hymenoptera appeared as long as 146 million years ago in the Cretaceous period, but achieved their wide diversity more recently in the Cenozoic era, which began 66 million years ago. A number of highly successful insect groups evolved in conjunction with flowering plants, a powerful illustration of coevolution.
Many modern insect genera developed during the Cenozoic. Insects from this period on are often found preserved in amber, often in perfect condition. The body plan, or morphology, of such specimens is thus easily compared with modern species. The study of fossilized insects is called paleoentomology.


Meganisoptera  (Protodonata)
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Meganisoptera is an extinct order of very large to gigantic insects, occasionally called griffinflies. The order was formerly named Protodonata, the "proto-Odonata", for their similar appearance and supposed relation to modern Odonata (damselflies and dragonflies). They range in Palaeozoic (Late Carboniferous to Late Permian) times. Though most were only slightly larger than modern dragonflies, the order includes the largest known insect species, such as the late Carboniferous Meganeura monyi, Megatypus, and the even larger early Permian Meganeuropsis permiana, with wingspans of up to 71 centimetres (28 in).
Most specimens are known from wing fragments only; with only a few as complete wings, and even fewer (of the family Meganeuridae) with body impressions. These show a globose head with large dentate mandibles, strong spiny legs, a large thorax, and long and slender dragonfly-like abdomen. Like true dragonflies, they were presumably predators.

Meganeuropsis
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Meganeuropsis is an extinct genus of griffinfly, order Meganisoptera, known from the Early Permian of North America, and represents the biggest known insect of all time. Meganeuropsis existed during the Artinskian age of the Permian period, 283.5–290.1 mya .The genus includes two described species:
Meganeuropsis permiana described in 1937 from Elmo, Kansas. It was one of the largest known insects that ever lived, with a reconstructed wing length of 330 millimetres (13 in), an estimated wingspan of up to 710 millimetres (28 in), and a body length from head to tail of almost 430 millimetres (17 in).
Meganeuropsis americana, discovered in Oklahoma in 1940, is most probably a junior synonym of Meganeuropsis permiana.It is represented by a forewing fragment 280 millimetres (11 in) long, which is conserved and displayed in the Harvard Museum of Natural History; the complete reconstructed wing had an estimated total length of 305 millimetres (12.0 in), making it the largest insect wing ever found (with a resulting wing span of 690 millimetres (27 in))

Meganeura
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Meganeura is a genus of extinct insects from the Carboniferous period (approximately 300 million years ago), which resembled and are related to the present-day dragonflies. With wingspans ranging from 65 cm (25.6 in) to over 70 cm (28 in),M. monyi is one of the largest-known flying insect species. Meganeura were predatory, with their diet mainly consisting of other insects.
First discovered in France in 1880, Meganeura is one of the largest known flying insects to ever exist. Although superficially similar to a dragonfly, Meganeura and others like it are generally referred to as griffinflies, due to morphological differences between them and the dragonflies.
It is generally considered that the maximum potential size of an insect is dictated by how much oxygen is available for respiration. The oxygen content of our atmosphere today is typically 21% of the total gases, but back in the Carboniferous it was much higher at up to 35%. Insects like Meganeura breathe through a system of tracheal tubes that carry oxygen directly into their internal tissues. A higher amount of oxygen in the atmosphere would supply a passive boost to these tissues with no effort on the part of Meganeura allowing for the larger growth. Falling oxygen levels after this period would mean that the giant insects simply did not have enough oxygen to maintain their size, resulting in either the evolution of smaller forms, or outright extinction of the larger.
Meganeura is likely to have hunted and fed in much the same way as dragonflies do today, although its larger size may suggest that many more creatures could have been on the menu for it. Aside from other invertebrates potential prey may have also included small amphibians that were rapidly evolving to terrestrial life.

Megatypus
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Megatypus is an extinct genus of insect of the order Meganisoptera. Species in this genus were much larger than their modern relatives, dragonflies and damselflies, and reached a wingspan of 70 centimeters (2.3 ft).


Palaeodictyoptera
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1.Manoblatta bertrandi 2.Meganeura monyi 3.Protophasma woodward 4.Palaeodictyoptera sp.

The Palaeodictyoptera are an extinct order of medium-sized to very large, primitive Palaeozoic paleopterous insects. They were characterised by beak-like mouthparts, and similarity, between their fore- and hind wings, and an additional pair of winglets (large paranotal lobes) on the prothorax, in front of the first pair of wings. Although the paranota are technically not wings, the Palaeodictyoptera are whimsically called "six-winged insects". The actual wings are often boldly marked, the colour patterns evident even in fossils.
The mouthparts were elongated, and included sharp piercing stylets, and possibly a sucking pump-like organ. Unlike modern sucking insects, such as the Hemipterans, the mouthparts were held vertically below the head, or projected forwards. They probably used these organs to suck juices from plants, although some may have been ectoparasites, or predators.

The largest-known insect of this order was Mazothairos, with a wingspan of up to 560 mm (22 in):
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Sawflies, wasps, bees, ants and allies (Hymenoptera)
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Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described,in addition to over 2,000 extinct ones.
The cladogram of external relationships, based on a 2008 DNA and protein analysis, shows the order as a clade, most closely related to endopterygote orders including the Diptera (true flies) and Lepidoptera (butterflies and moths).
Hymenoptera originated in the Triassic, with the oldest fossils belonging to the family Xyelidae. Social hymenopterans appeared during the Cretaceous.

The largest-known of this group was the giant ant Titanomyrma giganteum at 3 cm (1.2 in), with queens growing to 6 cm (2.4 in). It had a wingspan of 15 cm (5.9 in).
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Titanomyrma is a genus of prehistoric giant ant. The latest species to be discovered, T. lubei, was described in 2011, when a 49.5-million-year-old fossilized winged queen ant, comparable in size to hummingbirds, was found in Wyoming, United States. This fossil is the first fossil of a giant ant found in the Western Hemisphere. The presence of Titanomyrma in North America is considered to indicate "the first reported cross-Arctic dispersal by a thermophilic insect group".Another fossil species of this genus, T. gigantea, is the largest-known fossil or extant species of giant ant in the world.
Archibald in 2011 erected the genus Titanomyrma, described the species Titanomyrma lubei and proposed two new combinations, T. gigantea (formerly Formicium giganteum Lutz, 1986) and T. simillima (formerly F. simillimum Lutz, 1986). T. gigantea has been designated the type species for the genus.
The genus Titanomyrma is differentiated from others in the family by the shape of the gaster which is variable. In the three included species the gaster ranges from ovate to more slender or cylindrical. The A5 abdominal segment width relative to other gaster segments is variable and the relative lengths of A3–A7 are also variable.
The queens of the three Titanomyrma can be distinguished from those of other genera most easily by gaster characters. The gasters are more slender in Titanomyrma. Amongst the three species of Titanomyrma, the ratio between length to width of the queens of the three species is as follows, T. lubei – 2.14, T. gigantea – 1.40, and T. simillima – 1.50.The middle half of T. lubei is roughly cylindrical while for other Titanomyrma species, it is ovate with the segment A5 being the widest. The segment A3 has a length about a quarter of the width while for other species it is about a third. The segment A4 is thrice as long as the length of segment A3 while that of A4 segments of other species is less than twice. The segment A5–6 of T. lubei is approximately half as long as it is wide while for other species it is about a third. A3 is not curved around the petiole at the junction.
T. gigantea is the largest giant ant ever found, larger than the biggest extant giant ants, which are the five-centimetre-long (2.0 in) driver ants of the genus Dorylus, found in Central and East Africa.The fossils indicate that the males grew up to 3 centimetres (1.2 in) and the queens grew to 6 centimetres (2.4 in). It had a wingspan of about 15 centimetres (5.9 in)


Siphonaptera (Fleas)
Fleas are small flightless insects that form the order Siphonaptera. As external parasites of mammals and birds, they live by consuming the blood of their hosts. Adults are up to about 3 mm (0.12 in) long and usually brown. But before, there were big ...

Saurophthirus
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Saurophthirus is an extinct genus of flea that represents a transition between primitive stem fleas, and modern species. The type species, S. longipes is found in early Cretaceous strata of Baissa, Siberia. The second species, S. exquisitus, is from the Lower Cretaceous Yixian Formation.
Average length of specimens are 2.50 cm (1 in) long and is hypothesized to have sucked the blood of pterosaurs in the Cretaceous, in the way that bat fleas feed on bat blood today.







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Автор: valentint
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