New pollen morphotype from gut compression of a Cretaceous insect, and its bearing on palynomorphological evolution and palaeoecology

Plant remains from gut compressions of fossil insects are evidence of plant-insect interaction with implications for plant evolution and functional palynomorphology. We obtained pollen grains from compressed intestines of five xyelid species from the Lower Cretaceous Baisa locality, Transbaikalia, each with a single pollen morphotype in the pollen load. Among them, Ceroxyela dolichocera Rasnitsyn was loaded with the bilobed, monosaccate pollen grains Vitimipollis edulis Krassilov. A recently found specimen of the same species yielded a new pollen morphotype, Cryptosacciferites pabularis gen. et sp. nov., with ultrastructural evidence of a residual saccus, demonstrating a transition from saccate to asaccate morphologies. It is also unusual in having a well-developed lamellate apertural endexine as in some basal angiosperms. Although two individuals of Ceroxyela dolichocera studied for pollen load visited different plants, neither of them had mixed loads, which may suggest consecutive, rather than simultaneous, flowering of the source plants.