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Exceptionally preserved Late Albian (Cretaceous) Arcellaceans (Thecamoebians) from the Dakota Formation near Lincoln, Nebraska, USA

van Hengstum, P.J.; Reinhardt, E.G.; Medioli, F.S.; Gröcke, D.R.

Exceptionally preserved Late Albian (Cretaceous) Arcellaceans (Thecamoebians) from the Dakota Formation near Lincoln, Nebraska, USA Thumbnail


Authors

P.J. van Hengstum

E.G. Reinhardt

F.S. Medioli



Abstract

Thousands of exceptionally well-preserved Arcellaceans (Thecamoebians) have been recovered from a Late Albian (Cretaceous) deposit. Sedimentary samples were obtained from a clayey-silt leaf bed in the Dakota Formation, outcropping in a clay pit excavated by the Yankee Hill Brick Company, located near Lincoln, Nebraska. Based on recovered freshwater macrophyte spore and fossil remains, the leaf bed is a lagerstätten of paleobotanical remains in which the paleoenvironment has been interpreted as a quiescent freshwater setting. The large number of recovered thecamoebians revealed a high intraspecific variability in test morphology that is comparable to Holocene thecamoebian populations. Consequently, we employ the thecamoebian strain taxonomic framework, a first for ancient thecamoebians. Extant species contained in this collection include Difflugia oblonga, Difflugia protaeiformis, Difflugia urens, Pontigulasia compressa, Lagenodifflugia vas, Cucurbitella tricuspis, Lesquereusia spiralis and the cysts of environmentally stressed protozoans—with only one new species reported, Difflugia baukalabastron. The well-preserved nature of the taxa, suggesting little taphonomic bias, and the lack of significant new species supports the current hypothesis of minimal evolution in thecamoebian lineages through geologic time.

Citation

van Hengstum, P., Reinhardt, E., Medioli, F., & Gröcke, D. (2007). Exceptionally preserved Late Albian (Cretaceous) Arcellaceans (Thecamoebians) from the Dakota Formation near Lincoln, Nebraska, USA. Journal of foraminiferal research, 37(4), 300-308. https://doi.org/10.2113/gsjfr.37.4.300

Journal Article Type Article
Publication Date Oct 31, 2007
Deposit Date Jun 7, 2010
Publicly Available Date Aug 16, 2011
Journal Journal of foraminiferal research.
Print ISSN 0096-1191
Electronic ISSN 1943-264X
Publisher Cushman Foundation for Foraminiferal Research
Peer Reviewed Peer Reviewed
Volume 37
Issue 4
Pages 300-308
DOI https://doi.org/10.2113/gsjfr.37.4.300
Public URL https://durham-repository.worktribe.com/output/1563091

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