Planktonic foraminifera have been thoroughly studied due to their value as worldwide biostratigraphical markers. The scientific efforts led to the Chronos databases and the atlases on Eocene and Paleocene planktonic foraminifera as mentioned in the references. This key to planktonic foraminifera is our attempt to bring these outstanding scientific results in the understanding of Life on Earth to a broader public with an easy to use interface.

The design of the criteria and definition of the available values are inspired by "Petrizzo, M.R, Premoli Silva, I., Verga, D., 2011. Practical Manual of Cretaceous Planktonic Foraminifera. International School on Planktonic Foraminifera, 3rd Course 2004. New Revision 2011. Universities of Perugia and Milan" and the lectures of Maria Rose Petrizzo at the 6th. ISF Urbino. The two thumbnails for height of spire are from this source.

A glossary on the used terms and values is under development, but still in a preliminary state.   Michael Hesemann, April 2015.

for the Neogene:
Iaccarino, S., Premoli Silva, I., Biolzi, M., Foresi, L.M., Lirer, F., Turco E., 2007: Practical manual of Neogene planktonic foraminifera. International School on Planktonic Foraminifera.
Kennett, J. P., Srinivasan, M. S., 1983. Neogene planktonic foraminifera: A phylogenetic atlas.
Felix M. Gradstein, James G. Ogg, Mark D. Schmitz, and Gabi M. Ogg. The Geologic Time Scale 2012. [Oxford, U.K.]: Elsevier, 2012.
Kennett and Srinivasan, 1983 use N-Zones as time-markers, which are translated into absolute dates by using Gradstein et alt., 2012.
for the Eocene:
Pearson, P.N. et al. (eds.), 2006. Atlas of Eocene Planktonic Foraminifera. Cushman Foundation Special Publication 41.
for the Paleocone:
Huber et al., 1999. Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology 85.
for the Cretaceous:
MesozoicDB of Chronos as seen 2015.