Flowers and insects with in situ and/or adhered pollen from Eckfeld (Eocene) and Enspel (Oligocene), Germany

The Middle Eocene Eckfeld maar (c. 44 Ma) and the Late Oligocene Enspel crater lake (c. 24 Ma) localities, both in Germany, are renowned for the numerous well-preserved fossils they have yielded until the present day. Among these records, hundreds of angiosperm flowers have not been taxonomically affiliated. In addition, thousands of insects have also been recorded which potentially provide direct evidence for flower visitations and entomophilic pollination processes. To assign the flowers to a taxonomic system, we extracted in situ pollen from their anthers and studied them with light- (LM) and scanning electron microscopy (SEM). We also extracted pollen from fossil insects to obtain data on flower visits and possible pollinator roles. We investigated 943 buds/flowers/inflorescences from Eckfeld, of which 401 (c. 42.5%) contained in situ pollen. Based on the pollen processed so far, they represent at least 38 different angiosperm taxa. These include, among others, representatives from Anacardiaceae, Euphorbiaceae, Fabaceae, Menispermaceae, Onagraceae, Sapotaceae, and Vitaceae. We also studied 404 insect specimens from Eckfeld. These include 332 Coleoptera (19 with pollen), 43 Hymenoptera (13 with pollen), and 20 Diptera (1 with pollen). Within Coleoptera, pollen was most frequently associated with members of Sagrinae, a subfamily of leaf beetles (Chrysomelidae), and Agrilinae, a subfamily of jewel beetles (Buprestidae). Within Hymenoptera, the clade of corbiculate bees comprised most of the adhered pollen. From Enspel, we investigated 107 buds/flowers/inflorescences, of which 32 (c. 30 %) contained in situ pollen. Our analysis indicates that they represent around nine different angiosperm taxa. These include, among others, Malvaceae, Rosaceae, and Sapotaceae. So far, we have investigated 22 insect specimens (15 with pollen) from Enspel, including 17 Apidae (11 with pollen), one Blasticotomidae (with pollen), and a single Pamphiliidae (with pollen). These fossil records provide a unique insight into flower visitation during the Paleogene of Central Europe.