Сообщество, посвящённое ра - May 28th, 2014
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03:33 pm [industrialterro]
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Feilongus
Feilongus is an extinct genus of ctenochasmatoid or ornithocheiroid pterodactyloid pterosaur from the Barremian-Aptian-age Lower Cretaceous Yixian Formation of Beipiao, Liaoning, China. The genus was named in 2005 by Wang Xiaolin e.a.. The type species is Feilongus youngi. The genus name is derived from Feilong, the "flying dragon". The specific name honours the late Chinese paleontologist Yang Zhongjian or "Chung Chien Young". Feilongus is based on holotype IVPP V-12539, a skull and articulated mandible, with on the same plate the detached posterior braincase, of a subadult individual. The fossil is strongly crushed. It is notable for having two bony crests on the skull (one long and low on middle of the snout, and one projecting backwards from the rear of the skull), and for the upper jaws being 10% or 27 millimetres longer than the lower jaws, giving it a pronounced overbite. The preserved part of the second crest was short with the leading edge rounded, and may have had a nonbony extension, now lost. The skull of the only known individual is 390-400 millimeters long (15.4-15.7 inches) and extremely elongated with a slightly concave top. Its wingspan was estimated by Wang to have been around 2.4 meters (7.9 feet), making it large for a basal pterodactyloid. The skull and lower jaws held 76 long, curved needle-like teeth, eighteen in the upper, nineteen in the lower jaw, confined to the beak ends, the anterior third, of the jaws. A cladistic analysis by the describers showed Feilongus as the sister taxon of a clade consisting of Gallodactylus and Cycnorhamphus, meaning it was a member of the Gallodactylidae sensu Kellner, a group of ctenochasmatoids, within the larger Archaeopterodactyloidea, the clade containing according to Alexander Kellner the most basal pterodactyloids. The Ctenochasmatoidea are known for having numerous small, thin teeth, possibly for straining food from water, as flamingos do today. However, in 2006 an analysis by Lü Junchang had as outcome that Feilongus was not an archaeopterodactyloid, but a member of the Ornithocheiroidea sensu Kellner, closer to the Anhangueridae. This means that using the alternative terminology of David Unwin they are close to the Ornithocheiroidea sensu Unwin, a group the members of which are typically more adapted to soaring and a piscivore, or fish-eating, diet. Another publication following this general line of thought has put Feilongus and Boreopterus into a new ornithocheiroid family, the Boreopteridae. В Ляонине, северо-восточной области Китая, палеонтологи обнаружили окаменелости двух новых видов птерозавров. Feilongus youngi и Nurhachius ignaciobritoi разделяли небеса с ранними птицами 120 миллионов лет назад.
Feilongus имел два гребня на голове, бегущих от кончика "носа" до её задней части. Один гребень — в передней части морды, другой — в задней части головы. Этот птерозавр имел неправильный прикус, а его зубы были изогнутыми и иглообразными. А вот зубы Nurhachius ignaciobritoi были треугольными.
Оба вида принадлежат к группе, ранее найденной только в Европе.
Размах крыльев, затянутых тонкой кожей, у этих летающих ящеров составлял около 2,5 метров. Учёные предполагают, что этим видам был свойственен не машущий полёт, а парение.
Один из палеонтологов, опубликовавших новое большое исследование птерозавров, Александр Келлнер (Alexander Kellner) из федерального университета в Рио (Universidade Federal do Rio de Janeiro), сообщил любопытную подробность.
Он отметил, что пересекавшиеся во времени птерозавры и ранние птицы населяли, в массе своей, различные среды обитания и очень мало конкурировали друг с другом.
Птерозавры преобладали над птицами в прибрежных районах, в то время как птицы господствовали в глубине континента. Хотя и те, и другие, в принципе, встречались в каждом из этих биотопов.
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Tags: Вымершие рептилии, Мел, авеметатарзалии, архозавроморфы, архозавры, диапсиды, ктенохазматоидеи, монофенестраты, птеродактили, птерозавры
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04:03 pm [industrialterro]
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Geosternbergia
Geosternbergia from the Late Cretaceous geological period of North America, was one of the largest pterosaur genera and had a wingspan of up to 7.25 metres (23.8 ft). Geosternbergia was among the largest pterosaurs, with the wingspan of most adults ranging between 3 and 6 meters (9.8–19.6 ft). While most specimens are found crushed, enough fossils exist to put together a detailed description of the animal. Geosternbergia is distinguished from Pteranodon mainly by its upright-crest. The lower jaw of G. sternbergi was 1.25 meters (4 ft) long. The most distinctive characteristic of Geosternbergia is its cranial crest. These crests consisted of skull bones (frontals) projecting upward and backward from the skull. The size and shape of these crests varied due to a number of factors, including age, gender, and species. Male G. sternbergi, the older species of the two described to date, had a larger vertical crest with a broad forward projection, while G. maysei had a short, rounded vertical crest and was generally smaller. Females of both species were smaller and bore small, rounded crests. The crests were probably mainly display structures, though they may have had other functions as well. It was collected by George F. Sternberg in 1952 and described by John Christian Harksen in 1966, from the lower portion of the Niobrara Formation. It was older than Pteranodon longiceps and is considered by Bennett to be the direct ancestor of the later species. Geosternbergia fossils are known from the Niobrara and Sharon Springs Formations of the central United States. Geosternbergia existed as a group for more than four million years during the late Coniacian - early Campanian stages of the Cretaceous period. The genus is present in the lower the Niobrarra Formation except for the upper two; in 2003, Kenneth Carpenter surveyed the distribution and dating of fossils in this formation, demonstrating that Geosternbergia sternbergi existed there from 88-85 million years ago, while the species later named G. maysei existed between 81.5 and 80.5 million years ago. Geosternbergia was traditionally considered a species, or occasionally subgenus, of the similar pterosaur Pteranodon, in most major studies of pteranodontians through the 1990s. However, a 2010 review of the group by A.W.A. Kellner suggested that Pteranodon sternbergi was different enough from P. longiceps to belong in a distinct genus, to which Kellner also referred a new species, Geosternbergia maysei. Earlier, pterosaur researcher Chris Bennett had considered the G. maysei specimen an adult male P. longiceps. Adult Geosternbergia specimens may be divided into two distinct size classes, small and large, with the large size class being about one and a half times larger than the small, and the small being twice as common as the large. Both size classes lived alongside each other, and while researchers had previously suggested that they represent different species, Christopher Bennett showed that the differences between them are consistent with the concept that they represent females and males, and that Geosternbergia species were sexually dimorphic. Skulls from the larger size class preserve large, upward and backward pointing crests, while the crests of the smaller size class are small and triangular. Some larger skulls also show evidence of a second crest that extended long and low, toward the tip of the beak, which is not seen in smaller specimens. The gender of the different size classes was determined, not from the skulls, but from the pelvic bones. Contrary to what may be expected, the smaller size class had disproportionately large and wide-set pelvic bones. Bennett interpreted this as indicating a more spacious birth canal, through which eggs would pass. He concluded that the small size class with small, triangular crests represent females, and the larger, large-crested specimens represent males. Note that the overall size and crest size also corresponds to age. Immature specimens are known from both females and males, and immature males often have small crests similar to adult females. Therefore, it seems that the large crests only developed in males when they reached their large, adult size, making the gender of immature specimens difficult to establish from partial remains. The fact that females appear to have outnumbered males two to one suggests that, as with modern animals with size-related sexual dimorphism, such as sea lions and other pinnipeds, Geosternbergia might have been polygynous, with a few males competing for association with groups consisting of large numbers of females. Similar to modern pinnipeds, Geosternbergia may have competed to establish territory on rocky, offshore rookeries, with the largest, and largest-crested, males gaining the most territory and having more success mating with females. The crests of male Geosternbergia would not have been used in competition, but rather as "visual dominance-rank symbols", with display rituals taking the place of physical competition with other males. If this hypothesis is correct, it also is likely that male Geosternbergia played little to no part in rearing the young; such a behavior is not found in the males of modern polygynous animals who father many offspring at the same time. The Pteranodontidae are a family of large pterosaurs of the Cretaceous Period of North America. The family was named in 1876 by Othniel Charles Marsh. Pteranodontids had a distinctive, elongated crest jutting from the rear of the head (most famously seen in Pteranodon itself). The spectacularly-crested Nyctosaurus is sometimes included in this family, though usually placed in its own family, the Nyctosauridae (Nicholson & Lydekker, 1889). Modern researchers differ in their use of the concept. S. Christopher Bennett and Alexander Kellner have concluded that Nyctosaurus was not a pteranodontid. In 1994 Bennett defined a clade Pteranodontidae, also including species of the Anhangueridae. However, this definition has not been accepted by other workers. Alexander Kellner, for example, named several additional species for specimens previously classified as Pteranodon, and placed P. sternbergi in a distinct genus, Geosternbergia. Kellner re-defined Pteranodontidae as the most recent common ancestor of Pteranodon longiceps, Geosternbergia sternbergi and Dawndraco kanzai, and all of its descendants. This clade possibly includes the nyctosaurids. Analyses by David Unwin did indicate a close relationship between Pteranodon and Nyctosaurus, and he used the name Pteranodontia for the clade containing both.
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Tags: Вымершие рептилии, Мел, авеметатарзалии, архозавроморфы, архозавры, диапсиды, монофенестраты, орнитохейройды, птеранодонтиды, птеранодонтойды, птеродактили, птерозавры
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05:48 pm [industrialterro]
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Guidraco
Guidraco (Chin. gui (鬼) "malicious ghost" + Lat. draco "dragon") is an extinct genus of toothed pterodactyloid pterosaur known from the Early Cretaceous of Liaoning Province, northeast China. Guidraco is known only from the holotype IVPP V17083, an articulated partial skeleton consisting of a nearly complete skull, lower jaws and a series of four, second to fifth, cervical vertebrae. It was collected at Sihedang near Lingyuan City in the Liaoning Province from the Jiufotang Formation, dating to the Aptian stage of the Early Cretaceous, about 120 million years ago. Guidraco was first described and named by Wang Xiaolin, Alexander W.A. Kellner, Jiang Shunxing and Cheng Xin in 2012 and the type species is Guidraco venator. The generic name is derived from Chinese gui (鬼), "malicious ghost", and from Latin draco, "dragon". The specific name means "hunter" in Latin. The holotype skull of Guidraco has a length of thirty-eight centimetres. It is very elongated with a hollow profile but not very pointed as the upper edge and the line of the jaw run nearly parallel over most of their length. The ensuing relative robustness of the snout is reinforced by a short main skull opening, a fenestra nasoantorbitalis with just a quarter of skull length, and a lower jaw equalling the rostrum in depth. The snout lacks a crest. Above the eye sockets however, the line of the top of the snout curves steeply upwards, resulting in a very large crest on the frontals, as high as the posterior part of the skull is deep, ending in a rounded top. Due to the angling of the skull roof the crest slightly points forwards and its base extends to the back of the roof; however, the parietal is not part of it. In front of the crest large impressions of soft tissue are visible but these are plant remains. Further diagnostic features of the skull include an infratemporal fenestra with a narrow lower end, and a jugal of which the front branch extends no further than the front edge of the fenestra nasoantorbitalis. The teeth of Guidraco are very distinctive. Of the twenty-three teeth of the upper jaw the first is long and very narrow, pointing nearly horizontally forward. The next three teeth are enormous in size, very long, robust, pointed and slightly recurved. They gradually point more downwards. These are followed by a series of three medium-length downward-pointing straight teeth, of which the middle one, the sixth, is the shortest. The remaining thirteen teeth constitute a long row of small elements gradually diminishing in size. This arrangement is mirrored by the eighteen teeth of the lower jaw. Here however, a forward pointing tooth is lacking. The first four teeth are of great size, even longer than their counterparts of the upper jaw. Next is a series of three straight teeth of medium height, followed by a row of eleven increasingly smaller elements for a grand total in the head of eighty-two teeth. With the fossil, the beak is closed and due to their extreme length the front teeth extend far beyond the upper and lower edges of the head, the protruding parts being up to twice as long as the depth of the snout or lower jaw. The teeth can also be divided into two types according to their built: the first nine teeth of the upper jaw and eight teeth of the lower jaw have vertical ridges on the back of their enamel; the back teeth have a uniformly smooth enamel and thickened crown bases, giving them a more triangular outline. Though not having the form of a true rosette because the jaw ends were not expanded, the intermeshing front teeth functioned as a "prey grab" to catch slippery animals; the describers therefore consider Guidraco to have been a fish-eater. The neck vertebrae are moderately elongated, keeled and possess large pneumatic openings on their sides, the access by which the air sac of the neck could enter their hollow interiors. The axis bears a spiked spine. Guidraco was by the describers assigned to the Pteranodontoidea sensu Kellner. A phylogenetic analysis found it to be the sister taxon of the Brazilian Ludodactylus, the two species together forming a clade that was closely related to the Istiodactylidae and the Anhangueridae. The fact that a Chinese form is closely related to a South-American species would indicate a large faunal interchange between continents in this period. Китайская академия наук на днях опубликовала документы, согласно которым на северо-востоке страны ученые обнаружили останки птерозавра редкого типа, имевшего длинные зубы устрашающего вида.
Согласно опубликованным фотографиям, доисторическая летающая рептилия имела мощные челюсти и крупные резцовые зубы. Палеонтологи говорят, что найденный вид является довольно близким биологическим родственником вида Ludodactylus, останки которого в прошлом были обнаружены учеными на территории современной Бразилии.
Китайский палеонтолог Вон Сяолин говорит, что рядом с останками древнего ящера были найдены также и останки рыбы, что может свидетельствовать об употреблении в пищу этой рыбы незадолго до смерти птерозавра. Новый вид птерозавра получил научное название Guidraco venator.
Согласно данным исследователей, рептилия обитала на нашей планете в ранний меловой период - как раз в расцвет эпохи динозавров. Останки ящера были найдены на территории современной китайской провинции Ляонин, где ранее уже находили останки летающих ящеров.
Исследователи считают, что родство с бразильским птерозавром объясняется тем, что в ранний меловой период Азия и Южная Америка были расположены гораздо ближе друг к другу и мигрировать летающим ящерам с одного континента на другой было несложно. И тем не менее, считается, что впервые летающие ящеры появились именно в Азии, а уже оттуда распространились в другие регионы.
По предположению ученых, Guidraco venator вымер из-за нехватки пищи, а точнее из-за высокой конкуренции с другими, более сложноорганизованными видами.
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Tags: Вымершие рептилии, Мел, авеметатарзалии, архозавроморфы, архозавры, бореоптериды, диапсиды, монофенестраты, орнитохейройды, птеранодонтойды, птеродактили, птерозавры
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