Schwagerina

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Schwagerina
Temporal range: Permian
Scientific classification Red Pencil Icon.png
Clade: SAR
Phylum: Foraminifera
Class: Globothalamea (?)
Order: Fusulinida
Family: Schwagerinidae
Subfamily: Schwagerininae
Genus: Schwagerina
Von Muller, 1877

Schwagerina is an extinct genus of fusulinacean Foraminifera that is used as an Early Permian index fossil. The overall shape of the shell or test is fusiform to subcylindrical, the spirotheca, or outer test wall, is thick, and composed of tectum and alveolar keriotheca;[ clarification needed ] the septa are fluted throughout the length of the shell, intense to top of chambers in some, only in lower parts in others; axial fillings highly variable, chomata distinct or thin and discontinuous.

Tectum is the thin, dark, dense outer layer of the spirotheca, Keriotheca is the thicker, honeycomb-like alveolar, inner layer. Chomata are mounds secreted on the floor of the chamber that connect either side of the tunnel, which interconnects the chambers.

Daixina Ryzovskaya, 1949, is given (Loeblich and Tappan 1964) [1] as a synonym of Schwagerina.

Three genera are similar to Schwagerina, but differ in their internal details. They are:

Paraschagerina , Dunbar and Skinner 1939, from the Lower Permian. The spirotheca is structured as in schwagerina; the first two or three volutions tightly coiled and elongate-fusiform, the outer volutions distinctly inflated-fusiform; septa highly fluted throughout.

Pseudoschwagerina Dunbar and skinner, 1936, Lower Permia. Shell inflated-fusimform; first two or three volutions tightly coiled, outer ones inflated; spirotheca as in Schwaterina. Septa are fluted at the base, close speced at first, wide spaced later. Occidentoschagerina is given as a junior synonym.

Rugososchwagerina Milukho-Maklay, 1959, Upper Permian. Shell inflated-fusiform. First three or four volutions tightly coiled, elongate-fusiform, outer volutions greatly inflated. Spirotheca as with Schwagerina, moderately thin in the tightly coiled portion and next one or two volutions, becoming thick and more coarsely alveolar in the outer two or three. Septa are close spaced in the first three or four volutions, wide spaced in the next two or three, and again close spaced in the outermost.

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Spirocyclinidae is a family of foraminifera included in the order Loftusiida.

Spirocyclina is a genus of large forams, with a flat test as much as 10mm in diameter. Coiling is planispiral to slightly asymmetric and mostly involute, some becoming uncoiled with a straight final stage. The final whorl, or stage, has about 25 strongly arcuate chambers. Composition is of agglutinated matter, the outer layer of the wall imperforate. Chambers are subdivided into secondary chamberlets by internal structures. The aperture consists of a double row of pores on the apertural face. Anchispirocyclina and Martiguesia are among related genera.

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References

  1. Alfred R. Loeblich Jr and Helen Tappan, 1964. Sarcodina Chiefly "Thecamoebians" and Foraminiferida; Treatise on Invertebrate Paleontology, Part C Protista 2. Geological Society of America and University of Kansas Press.

Further reading