A combined light and scanning electron microscopy study.

The uppermost Eocene Florissant Formation, Rocky Mountains, Colorado, has yielded numerous insect, vertebrate and plant fossils. Three previous comprehensive palynological studies investigated sections of lacustrine deposits of the Florissant Formation and documented the response of plant communities to volcanic eruptive phases but overall found little change in plant composition throughout the investigated sections. These studies reported up to 150 pollen and spore phenotypes. In the present paper, we used a taxonomic approach to the investigation of dispersed pollen and spores of the Florissant Formation. Sediment samples from the shale units containing macrofossils were investigated using light microscopy (LM) and scanning electron microscopy (SEM). The general picture of the palynoflora is in agreement with previous studies. However, the combined LM and SEM investigation provides important complementary information to previous LM studies. While a fairly large amount of previous pollen determinations could be confirmed, the purported taxonomic affinities of several pollen phenotypes need to be revised. For example, pollen referred to asPodocarpusorPodocarpiditessp. belongs to the PinaceaeCathaya, Malus/Pyrusactually belongs to Dryadoideae, pollen of the form genusBoehlensipollisreferred to as Proteaceae/Sapindaceae/Elaeagnaceae orCardiospermumbelongs to Sapindaceae but not toCardiospermum, and pollen ofPersicarioipollissp. B with previously assumed affinities to Polygonaceae actually belongs to Thymelaeaceae.Pandaniiditesand one type ofMalvacipolliscannot be linked with Pandanaceae and Malvaceae. A few taxa are new records for Florissant (Ebenaceae:Diospyros; Mernispermaceae; Trochodendraceae:Tetracentron). In general, SEM investigations complement the LM palynological studies and improve the identification of dispersed pollen and spores and enable integration of data from dispersed fossil pollen into a wide range of comparative morphological, taxonomic, evolutionary, biogeographic and phylogenetic studies. [ABSTRACT FROM AUTHOR]