real viagra online
buy real viagra online no prescription
| real viagra online|
268-buy real viagra online no prescription
buy real viagra online no prescription-260
260 to 251 million years ago
The Lopingian constitutes the last subdivision of the Permian, following the . It is divided into two unequal epochs, the long and the short (only about 2 million years) . The Lopingian, Wuchiapingian and Changhsingian are named after Chinese localities where fossils and rock strata of this age occur in a good and mostly unbroken series. As part of the current revision of Permian stratigraphy, "Lopingian" and "Guadalupian" have replaced earlier terms like "Upper Permian", "Zechstein", "Tartarian", and "Dzulfinan" in international usage (although the latter three terms are still applied locally).
The Lopingian epoch lasted about as long as the preceding Guadalupian, approximately 9 million years. This was a period of great stress for eco-systems, as the climate continued to dry and the single large continent of did not provide much room for diversity (the more isolated islands and continents, the more species). Throughout the Permian period the numbers of invertebrate species tends to decrease. At the end of the Lopingian there is a period of enormous vulcanism (in what is now ), which further stresses ecosystems by introducing acid rain into the atmosphere. Finally, at the end of the period there appears to have been either a tremendous period of vulcanism or an extraterrestrial impact (possibly a comet or giant asteroid similar to the one that killed the dinosaurs), as 95% of species of living beings suddenly die out within a very short period. The era comes to an end and new species inherit the globe.
buy real viagra online
In the dry late Permian environment many types of and flourished. The giant and of the Middle Permian had vanished, but the big were still around, sharing the world with various types of more advanced therapsids that had likewise survived, including the large like Gorgonops the small to medium-sized , the newly evolved and very mammal-like like Procynosuchus, and an astonishing diversity of herbivorous . A great many small insectivorous lizard-like reptiles, like Paliguana, inhabited the landscape, most of which, curiously, had hind-legs much longer than their forelimbs (clearly an adaptation to bipedal locomotion, like the frill-necked lizard of Australia today). Finally, the basal tetrapods, although reduced in numbers, were nevertheless present and included animals of large size. The aquatic rhinesuchid and capitosaurian were clearly the successors of the Middle Permian melosaurs and early Permian eryopids, both of which they resembled closely in size, appearance, and no doubt habits as well.
As the biggest animals around, the fearsome looking, but herbivorous, pareiasaurs were nevertheless not free of danger. They had outlasted the carnivorous dinocephalians, but now the previously small and insignificant gorgonopsians had evolved to large forms (up to the size of a modern lion or bear) to take their place. These animals, the equivalent of the sabre-toothed cat of the era, used their enormous canines to bring down the ox- to rhino sized pareiasaurs. Gorgonopsians and pareiasaurs may even have formed a "co-adaptive pair" (like the Smilodon-mammoth 'relationship' of the Pleistocene); the gorgonopsians evolved in larger, more robust and larger fanged forms (for example Dinogorgon and Inostrancevia) whereas their pareiasaur prey become more armoured (for example Pareiasaurus and Scutosaurus). Both groups became simultaneously extinct and the end of the Permian.
Although they had an obsolete body design by the time their apex ended a few species of the managed to hold out until this period, by which time their descendants had truly taken over from them.
buy real viagra online
page uploaded on Kheper Site on 24 August 2000, page uploaded on Palaeos Site 10 April 2002,
last modified ATW060121, MAK090514
original text content by M. Alan Kazlev 2000-2002
this material may be freely used for non-commercial purposes