Gyroidinoides nitida, copyright Dieter Ketelsen.

Belongs within: Rotaliida.

The Osangulariidae are a group of trochospiral Foraminifera known from the Lower Cretaceous to the present (Loeblich & Tappan 1964b).

The Osangulariidae: deep-water trochospires
Published 21 January 2013
Dorsal (spiral side), lateral and ventral (umbilical side) views of an Osangularia specimen, from here.

For today’s post, I’m presenting for your consideration the Osangulariidae, a family within the rotaliid Foraminifera. These are benthic forams, mostly found in intermediate waters within the top few centimetres of sea floor sediment (Kaiho 1998). The Osangulariidae were first established as a distinct family of Foraminifera by Loeblich & Tappan (1964) to include trochospiral forams with bilamellar walls, with an important distinguishing feature separating osangulariids from related families being their granular rather than radial test wall structure. However, Loeblich & Tappan were criticised by Kaiho (1998) for their utilisation of this character. In developing a more lineage-based classification of the osangulariids and related taxa, Kaiho concluded that “radial-granular texture has no taxonomic significance in the suprageneric classification of calcareous trochospiral benthic foraminifera”. Instead, Kaiho defined the Osangulariidae as trochospiral forams with an aperture on the umbilical side of the test, an angular periphery and strongly oblique sutures on the spiral side.

The Coniacian (Late Cretaceous) Globorotalites multisepta, from Loeblich & Tappan (1964).

The Osangulariidae first appeared in the Early Cretaceous, during the Aptian epoch. Kaiho (1998) recognised two subfamilies within the Osangulariidae, the Osangulariinae and the Globorotalitinae (not to be confused with the Globorotaliinae), regarding the slightly earlier-appearing Globorotalitinae as probably ancestral to the Osangulariinae. The Globorotalitinae possessed a test with a strongly inflated umbilical side, and can basically be described as looking like a jelly mould. Osangulariids of the globorotalitine type became extinct during the Palaeocene.

Nuttallides rugosus, from Todd 1965.

The Osangulariinae, on the other hand, have survived to the present day. Their most obvious distinction from the Globorotalitinae is the reduction of the umbilical side of the test, so that osangulariines tend to be more discus-shaped than jelly-mould-shaped. The earliest osangulariine genus, Protosangularia, appeared in the Aptian and survived until the Cenomanian in the early Late Cretaceous. At the end of the Cenomanian, a major anoxic event took place in the ocean followed by a reduction in world ocean temperatures. After this, Protosangularia was replaced by a number of other osangulariine genera appearing from the Turonian to the early Campanian (Kaiho 1998). Two of these genera, Osangularia and Nuttallides, are the family’s modern representatives.

Systematics of Osangulariidae

Characters (from Loeblich & Tappan 1964b): Test trochospiral; wall calcareous, perforate granular in structure, bilamellar; aperture with interiomarginal portion and vertical or oblique portion extending up apertural face, two parts may be joined or distinct separate openings, areal opening may be multiple.

    |--Charltonina Bermúdez 1952LT64
    |    `--*C. madrugaensis (Cushman & Bermúdez 1948) [=Pseudoparrella madrugaensis]LT64
    |--Cribroparrella Ten Dam 1948 [=Cribroparella, Dribroparella]LT64
    |    `--*C. regadana Ten Dam 1948LT64
    |--Goupillaudina Marie 1958LT64
    |    `--*G. daguini Marie 1958LT64
    `--Osangularia Brotzen 1940 [incl. Parrella Finlay 1939 non Ginsburg 1938]LT64
         |--*O. lens Brotzen 1940LT64
         |--O. bengalensis (Schwager 1866) [=Anomalina bengalensis, *Parrella bengalensis]LT64
         |--O. californicaBL79
         |--O. culterJW99
         `--O. infracretaceaBL79

*Type species of generic name indicated


[BL79] Basov, V. A., B. G. Lopatin, I. S. Gramberg, A. I. Danjushevskaya, V. Ya. Kaban’kov, V. M. Lazurkin & D. K. Patrunov. 1979. Lower Cretaceous lithostratigraphy near Galicia Bank. Initial Reports of the Deep Sea Drilling Project 47: 683–717.

[JW99] Jian, Z.-M., L.-J. Wang, M. Kienast, M. Sarnthein, W. Kuhnt, H.-L. Lin & P.-X. Wang. 1999. Benthic foraminiferal paleoceanography of the South China Sea over the last 40,000 years. Marine Geology 156: 159–186.

Kaiho, K. 1998. Phylogeny of deep-sea calcareous trochospiral benthic Foraminifera: evolution and diversification. Micropaleontology 44 (3): 291–311.

[LT64] Loeblich, A. R., Jr & H. Tappan. 1964. Sarcodina: chiefly “thecamoebians” and Foraminiferida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt C. Protista 2 vol. 2. The Geological Society of America and The University of Kansas Press.

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