Hyperamminids: A Rough Retort

Hyperammina elongata, photographed by Onno Groß.

Agglutinated foram time again! In previous posts, I've described how these aquatic amoeboids construct coverings for themselves by cementing together particles from the surrounding environment. In the family of forams I'm presenting you with today, the Hyperamminidae, their choice of particle is generally sand grains, glued together with a relatively small amount of cement. As a result, hyperamminids often have a quite rough appearance to their walls. They live free, not cemented to their substrate. The test is not divided into chambers; instead, it starts as a globular chamber (the proloculus) that opens into an elongate tube. The overall appearance, therefore, is not dissimilar to one of those glass cylinders with a basal bulb (like an old thermometer). In species of Hyperammina, the tube is simple and tapers as it gets further from the proloculus. In contrast, the genus Saccorhiza has the tube more constant in diameter, and also has the tube branching dichotomously (Loeblich & Tappan 1964). Hyperamminids are abundant in the deep sea, and though certainly not among the largest forams, they can easily be a millimetre or more in size.

Agglomeration of Saccorhiza ramosa tubes, from here.

The classification of agglutinated forams presented by Kaminski (2004) lists six genera in the Hyperamminidae, with separate subfamilies for Hyperammina and Saccorhiza. These two genera are the only ones alive today; the remainder are all fossils. The record of hyperamminids stretches back some way: specimens have been assigned to Saccorhiza from the Lower Carboniferous, while Hyperammina is recorded from as far back as the Lower Ordovician. Yep, that's a single genus that goes back nearly 500 million years (really makes you wish that meant something). The genus Platysolenites, if correctly placed within the hyperamminids, is one of the oldest of all forams, known from the very early Cambrian. The other genera are also Palaeozoic; one of them, Sacchararena, had a test made with fine white sand, leading to its name: 'sugar sand' (Loeblich & Tappan 1984).

REFERENCES

Kaminski, M. A. 2004. The Year 2000 classification of the agglutinated Foraminifera. In: Bubík, M. & M. A. Kaminski (eds) Proceedings of the Sixth International Workshop on Agglutinated Foraminifera. Grzybowski Foundation Special Publication 8: 237-255.

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.

Loeblich, A. R., Jr & H. Tappan. 1984. Some new proteinaceous and agglutinated genera of Foraminiferida. Journal of Paleontology 58 (4): 1158-1163.