A new genus and species of hemeroscopid dragonfly, Abrohemeroscopus mengi gen. et sp. nov., of the family Hem-eroscopidae Pritykina, 1977, from the Lower Cretaceous Jiufotang Formation, Liaoning Province, Northeastern China, is de-scribed and illustrated. This new genus is rather similar to Hemeroscopus Pritykina, 1977, but differs from the latter in the fol-lowing characters: (1) hindwing anal loop is smaller, only with 6 - 7 cells (plesiomorphy); (2) Rspl is absent (plesiomorphy);(3) the hindwing vein CuAa is curved and has five distinct posterior branches (plesiomorphy); (4) the forewing MP is not short-ened, reaching the posterior wing margin slightly beyond the level of the nodus (plesiomorphy); (5) pterostigmata more distinct-ly braced (plesiomorphy); (6) the hindwing area between MP and CuAa is nanow, with only one row of cells near the discoidaltriangle ( plesiomorphy). This is the oldest fossil record of the Hemeroscopidae in China.%本文记述昼蜓科化石一新属新种--孟氏丽昼蜓Abrohemeroscopus mengi gen.et sp.nov..化石采自辽宁省义县早白垩世九佛堂组地层中.新属与巴依萨昼蜓Hemeroscopus Pritykina,1977在形态上比较相似,但在演化程度上更为原始,主要体现在下面几个方面:(1)后翅臀套较小,仅有6～7个翅室;(2)径增脉(Rspl)缺;(3)后翅CuAa脉弯曲,带有5个明显的后分支;(4)前翅MP脉不显短,终止于翅后缘近翅结处;(5)翅痣下有一个明显的支脉;(6)后翅CuAa和MP域基部较窄,在三角室下方仅有1排翅室.这是昼蜓科化石在中国的最老记录.
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