Abstract The paper overviews the fossil record of insects with long mouthparts and rostra adapted to feeding on floral nectar and pollination drops of extinct gymnosperms. The presence of suctorial mouthparts is demonstrated for the first time for the Permian mecopterans Permochoristidae and Permotanyderidae. The long-proboscid scorpionflies Mesopsychidae are recorded for the first time from the Upper Jurassic of Kazakhstan. A new finding of a detached head of a long-proboscid nectar-feeding brachyceran fly is reported from the Lower Cretaceous of Transbaikalia. Three major radiations of long-proboscid nectar feeders are identified: the Paleozoic, the Mesozoic, and the Cenozoic one; they were related to the Paleozoic seed ferns, the Bennettitales and other Mesozoic entomophilous gymnosperms, and the flowering plants, respectively. The earliest long-proboscid nectar feeders, found in the Lower Permian deposits of the Cis-Urals, belong to Protomeropidae (stem-Amphiesmenoptera). The few other Paleozoic insects specialized to nectarivory probably also included some long-proboscid Permochoristidae. The diversity of long-proboscid nectar feeders shows a dramatic increase since the Middle Jurassic. About 70 Mesozoic species with preserved long mouthparts and rostra are known to date; they belong to 12 families and 3 orders (Mecoptera, Neuroptera, and Diptera) and can be clustered into three morphogroups. With the beginning of the Cenozoic the long-proboscid Mecoptera and Neuroptera were supplanted by Hymenoptera and Lepidoptera in the nectar-feeding niche, while Diptera on the whole retained this specialization. Considerable abundance of long-proboscid nectar feeders before the appearance of flowers with hidden nectar indicates that complex pollination systems first evolved in gymnosperms. Therefore, insect pollination cannot be considered the key novelty in flowering plants crucial for their evolutionary success.
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