Fascinorbis gen. nov., a new genus of Stephanodiscaceae (Bacillariophyta) from a Late Miocene lacustrine diatomite

Abstract

We used light and electron microscopy to characterize a Late Miocene freshwater diatomite deposit in the Chalk Hills Formation, near Payette, Idaho, USA. The diatom assemblage from this sample was nearly monotypic, dominated by a single taxon with similarities to Lindavia bodanica (Thalassiosirales) but with several features uncharacteristic of the genus Lindavia, such as a rimoportula(e) on the valve mantle located on a costa, simple alveolar structure, and spines at the external valve face-mantle junction. A combination of other characters for this species complicate its placement into existing genera, including a lack of central fultoportulae, central area with loculate areolae with domed cribra, and a single ring of mantle fultoportulae with three satellite pores with well-developed cowlings and broad satellite pore covers. Based on this unique set of features, we have established a new genus, Fascinorbis, which appears to represent an important transitional form in the evolution of the Lindavia lineage.

Keywords:

• Lindavia
• fossil
• taxonomy
• extinct
• Thalassiosirales
• Cyclotella

Acknowledgements

We thank the Idaho Geological Survey for access to materials used for this analysis. Diatomite samples were collected by members of the Idaho Geological Survey (Reed Lewis and Renee Love). We also thank Andrea Shilling for assistance with SEM imaging and initial sample descriptions, Helena Bierly for assistance with sample processing and slide preparation, and Mike Wynne (University of Michigan) for help with nomenclature.

Disclosure statement

No potential conflict of interest was reported by the author(s).