Field of Science

The Forams that Bind

Cross-section of Fabiania cassis, from BouDagher-Fadel (2008).


Here we see an example of Fabiania. Fabiania is a genus of foraminiferan known from the Eocene epoch that could reach a relatively large size as forams go, up to several millimetres across (nowhere near as large as some that I've covered on this site, maybe, but still respectable). It had a conical test with a rounded apex and a deeply excavated centre; depending on growing conditions, individual Fabiania might be a regular or a flattened cone. In its early stage, Fabiania had two globose thick-walled and perforate chambers; later chambers were cyclical and divided by horizontal and vertical partitions. The aperture of the test was a single row of pores opening into the large umbilicus. The wall of the test was thick and calcareous, and covered with coarse perforations on the upper side of the cone (BouDagher-Fadel 2008; Loeblich & Tappan 1964).

Fabiania lived in association with coral reefs, often preferring the undersides of corals and other sheltered locations. It was primarily found around the mid-depths, not too close to the water's surface but also not too deep (Bosellini & Papazzoni 2003). I've referred in an earlier post to another group of coral-encrusting forams, the acervulinids. Because reef forams tend to be cryptic (in more exposed parts of the reef they tend to get out-competed by coralline algae), and are often variable in morphology making them taxonomically difficult, they tend to be less studied than the reef's more prominent components. However, forams may play a not so insignificant role in developing the reef's structure, helping to bind the reef in place.

REFERENCES

Bosellini, F. R., & C. A. Papazzoni. 2003. Palaeoecological significance of coral-encrusting foraminiferan associations: a case-study from the Upper Eocene of northern Italy. Acta Palaeontologica Polonica 48 (2): 279–292.

BouDagher-Fadel, M. K. 2008. The Cenozoic larger benthic foraminifera: the Palaeogene. Developments in Palaeontology and Stratigraphy 21: 297–418.

Loeblich, A. R., Jr & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina, chiefly "thecamoebians" and Foraminiferida vol. 1. The Geological Society of America and The University of Kansas Press.

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