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''Megarachne servinei'' is an extinct eurypterid found in Upper Carboniferous (Pennsylvanian)-aged freshwater strata near Córdoba, Argentina. ==Discovery== ''Megarachne servinei'' was originally described in 1980 by the Argentinean palaeontologist Mario Hünicken. The holotype was recovered from the Pallero Member of the Bajo de Véliz Formation of Argentina, a locality dated to the Asselian Age ( to million years ago (Ma)).〔(【引用サイトリンク】title=Megarachne servinei )〕 Hünicken wrongly identified the specimen as a mygalomorph spider based on the shape of the carapace, the wide circular eye tubercle located between the two eyes in the center of the head, a structure in front of the carapace he identified as spatulate chelicerae, and a circular structure behind the first body segment which he identified as the "moderately hairy" abdomen. Hünicken's identification relied heavily on X-ray microtomography of the holotype, and additional hidden structures were also extrapolated from the X-radiographs.〔 With a legspan estimated to be , this would have made ''Megarachne servinei'' the largest spider to have ever existed, far exceeding the goliath birdeater (''Theraphosa blondi'') which has a maximum legspan of only around . The discovery quickly became popular and various exhibits with reconstructions of ''Megarachne servinei'' as a gigantic spider were set up in museums around the world.〔 The identification of the specimen as a spider was doubted by some arachnologists. Even Hünicken himself acknowledged discrepancies in the morphology of the fossil that could not be accommodated with an arachnid identity. However, the holotype was by then deposited in a bank vault and other paleontologists had access only to the plaster casts.〔 In 2005, a second, more complete specimen was recovered from the same locality and horizon. A research team led by the British paleontologist and arachnologist Paul A. Selden and consisting of Hünicken and Argentinean arachnologist José A Corronca reexamined the holotype in light of the new discovery. They concluded that ''Megarachne servinei'' was not a spider, but was in fact, a large eurypterid,〔〔 an extinct group of chelicerates more commonly known as "sea scorpions" and related to spiders, true scorpions, and horseshoe crabs. A morphological comparison with other eurypterids indicated that ''Megarachne'' most closely resembled another large Permo-Carboniferous eurypterid, the hibbertopteroid ''Woodwardopterus scabrosus'' which is known only from a single specimen.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Megarachne」の詳細全文を読む スポンサード リンク
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