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Freshwater diatom floras from Pre-Neogene times are rare, known from only a few localities, and tend to have limited taxonomic diversity. The late Eocene lacustrine beds of the Florissant Formation in Colorado provide an exceptionally well-preserved record, having yielded the most genus-rich of the early freshwater diatom floras. With its 34 million-year age, the flora represents the geologically earliest documented occurrence of many modern freshwater genera and includes taxa with strong affinities to extant species.
This monograph illustrates and describes the Florissant diatom flora from the Clare’s Quarry site that includes species and morphotypes of 21 genera. Among them are 5 newly-named species: Aulacoseira clarensis, Platessa florissantia, Navicula eomenisculus, Adlafia tellerensis, and Frustulia coloradensis; and one new variety: Fragilaria vaucheriae var. lohmanii.
34 plates, an exhaustive reference list and indices of taxa round up this volume and make it a valuable source of information for biologists and palaeontologists working on fossil diatom floristics.