Three dimensional reconstructions of Nummulites tests reveal complex chamber shapes

Larger benthic foraminifera (LBF) are an important tool for the biostratigraphy of (sub)tropical shallow marine deposits. In Paleogene the genus Nummulites is an important genus for biostratigraphical zonation schemes. However, classification is Europe centered and based on external characters and equatorial thin sections. New results from regions outside the northern Tethys shows that a more rigid framework for the classification of nummulites is needed.

Here we present a new tool for achieving this goal. We visualise 3D chamber shape of Nummulites djodjokartae and compare these to traditional morphometrical characters. To achieve this goal we use computed microtomography of well preserved Nummulites tests.

We find that despite the regular shape in equatorial and axial thin section 3D chamber shape is not predicted by these sections. We argue that 3D reconstructions of Nummulites tests will be a great aid in improving our understanding lineages within the genus Nummulites, and to elucidate its evolutionary and biogeographical history.