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The Tipulidae s.l.—craneflies—are one of the largest groups of the Diptera containing over 15,270 valid species and subspecies. The immatures of the majority of species live in aquatic or semiaquatic habitats. Some aquatic species live entirely submerged and lack functional spiracles, others come to the surface to take oxygen by using spiracles positioned at the end of the abdomen. Semiaquatic species occur in a wide range of habitats. The semiterrestrial and terrestrial larvae live in environments that are moist or at least humous. All adult craneflies are terrestrial. Conflicting hypotheses on the phylogenetic position of the Tipuloidea within the Diptera continue to exist: some authors consider them to represent one of the oldest lineages of the Diptera, others suppose a close relationship to the Brachycera, the true flies. Current systematic knowledge of the Tipuloidea indicates that the Palaearctic region contains the highest number of genus-group taxa, while the Neotropical region has the highest number of species and subspecies. The Afrotropical and Australasian regions are relatively poor respectively in genera and subgenera and in species and subspecies. The oldest fossils that represent the Tipuloidea date back to the Lower Triassic at about 240 million years. Present-day general distribution patterns of many higher taxa of Tipuloidea probably have a Pangean or Gondwanan origin. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment.  相似文献
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