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22.07.2016 23:15 - A Complete Encyclopedia Of The Largest Prehistoric Animals Vol.2 Insects part2 Myriapoda and Siphonaptera
Автор: valentint Категория: Други   
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Myriapoda
image1.
Amynilyspes 2. Zanclodesmus 3. Arthropleura 4. Hexecontasoma 5. Gaspestria
Nearly 13,000 species of arthropod are classified in the Myriapoda, the "many-legged ones." All myriapods are terrestrial forms. Like insects and other uniramian arthropods, myriapods have appendages with only one branch, or ramus. Myriapods can have anywhere from fewer than ten to nearly 200 pairs of appendages; they range in size from nearly microscopic to 30 cm in length. Most myriapods live in humid environments, and can be found in soils, in leaf litters, or under stones and wood. Many species possess repugnatorial glands, specialized glands that secrete foul-tasing compounds and thus function in defense. There are four groups of myriapods; how they are related to each other is not yet well understood. Two of them, the Symphyla and Pauropoda, consist of tiny arthropods living in leaf litter and soil; both superficially resemble centipedes. The Chilopoda includes the true centipedes, like the one shown at the top left of this page. Chilopods have only one pair of legs per body segment. They are predators; the first pair of appendages on the trunk are modified into a pair of claws with poison glands, which centipedes use to capture prey (usually other arthropods). The bite of large centipedes can cause humans some pain and discomfort, although there are no authenticated cases of human fatalities from centipede bites.
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Myriapods in the Diplopoda ("double legs") include the millipedes, like the one pictured at the top right of this page. Millipede segments are formed in early development by fusion of two adjacent embryonic segments; thus, each adult segment of a millipede bears two pairs of legs. Unlike the predatory Chilopoda, most millipedes feed on decaying vegetation, although some are carnivorous.
Because most myriapods have a thin, light cuticle and live in environments where fossilization is unlikely, the fossil record of myriapods is quite sparse. Enough remains, however, to show that the group is a very old one indeed. The oldest fossil uniramians are myriapod-like marine organisms from the Cambrian. Some fossil burrows from the Ordovician have been claimed as myriapod burrows; this speculation is hard to test, but if it is correct, then myriapods might have been living on land as early as 400 million years ago. The oldest definite body fossils of myriapods come from the Late Silurian, though the oldest centipedes come from the Devonian-age Gilboa Forest of New York. A few more myriapod are known from the Devonian and Carboniferous (like the fossil millipede shown below, from the Pennsylvanian-age Mazon Creek deposits of Illinois) and from Cenozoic amber.


Arthropleura
armata is the biggest arthropod of all time
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The giant extinct invertebrate Arthropleura resembled some modern millipedes, but could grow to be more than one-and-a-half feet wide, and may sometimes have been more than six feet long.
Arthropleura is a contender for the biggest arthropod of all time, and like with other arthropods of the Carboniferous period, this gigantism has been attributed to the greater abundance of oxygen in the atmosphere of this time. Many fossilised track ways have also been preserved with some even showing Arthropleura moving around trees as it made its way through the Carboniferous forests.
Because the mouth of Arthropleura has never been recovered it is has been difficult to say with certainty if it was a herbivore or carnivore. Instead scientists have had to look at the digestive tract and coprolites of this animal, which have been found to contain spores from plants like ferns, something that is not seen in a carnivorous animal suggesting it was a herbivore.
Arthropleura disappears from the fossil record during the early Permian when the climate dried and the lush forests were replaced with arid and desert like environments. Not only did the oxygen content become reduced from the lack of oxygen producing vegetation, the dry conditions would not have suited Arthropleura because of its crustacean ancestry. Crustaceans as a whole need moist conditions to stop themselves from drying out which is why today you either see them in aquatic environments, or the shaded areas of the ground such as amongst the leaf litter where the ground cannot get dried out by the sun.


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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