Organism · Foraminifera
Nummulites laevigatus
Source time context (not species duration) · ≈ 56–33.9 Ma
Inferred life reconstruction
Nummulites laevigatus
Overview
Nummulites laevigatus is a foraminifer that produced a hard shell. Although it resembles a small animal’s shell, its maker was a single cell. Its rounded outline offers a starting point for the story of Eocene seas.[1][3]
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Key facts
The natural history museum in Paris holds five syntypes of this species. They are complete shells with bulging centers. Comparing several side by side provides a starting point for understanding the species’ form.[1]
Time and place
This foraminifer lived in the Eocene, a period roughly 56–34 million years ago. Museum specimen FA119 came from Laon in present-day Aisne, France. A bed named after the species in southern England has also been used to study Eocene marine environments.[1][4]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
The shells in FA119 have convex centers. A separate specimen lot, FA118, is recorded as having an almost spherical outline. Comparing the heights of rims and centers reveals variation among shells recorded as the same species.[1][2]
Nummulites laevigatus is a foraminifer with a coin-shaped shell. A 2008 reassessment of the Hantken collection reported diameters of approximately 6–7 mm for specimens identified as A-forms.[9]
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Habitat and reproduction
Foraminifers are single-celled organisms widespread in marine and brackish waters. Research on the Laevigatus Bed in southern England describes a shallow continental-shelf environment flooded by the returning sea. Accumulations of tiny shells can thus help researchers read changes in ancient shorelines.[3][4]
Fossil discovery
The museum record for FA119 also cites illustrations in an 1853 publication. Old literature and preserved specimens are linked. Reexamining a shell can connect centuries of natural-history records.[1]
References
- MNHN — Nummulites laevigatus specimen FA119
- MNHN — Nummulites laevigatus specimen FA118
- British Geological Survey — The body and life of foraminifera
- Murray & Wright — Palaeogene Foraminiferida
- Taverne & Gayet2006 — Redescription of Halecopsis insignis
- MNHN — Nummulites laevigatus specimen FA119
- Murray & Wright — Palaeogene Foraminiferida
- British Geological Survey — The body and life of foraminifera
- Kecskeméti (2008) — Reassessment of the Hantken Nummulites collection
Research questions
What might the degree of swelling at a shell’s center reveal? Comparing outer form and internal structure across specimens leads to questions about growth and species distinctions. A complex structure made by a single cell offers much to investigate.[1][2][3]
Observation
Move your gaze from the rounded rim to the convex center. Remember that the maker of the hard shell was a single cell.[1][2][3][4]
Related organisms
Osmeroides insignisRay-finned fishesSource time context (not species duration) · ≈ 56–33.9 MaFish and foraminifers of Eocene European seas
Osmeroides and Nummulites offer different ways into the seas of Eocene Europe. Connect fish records and foraminiferal shells from places such as England and France to compare different sizes and body organizations.