Astrononion is a genus of foraminifera in the family Nonionidae, characterized by an evolute planispiral test with radially stellate structures partly covering the sutures on either side. The test is free, bilaterally symmetrical; periphery broadly rounded; chambers distinct, separated by depressed radial sutures, increasing gradually in size, and usually inflated; aperture a low arched opening at the base of the face of the test. The wall is of finely perforate monolamellar granular calcite.
| Astrononion Temporal range: M Eocene - Recent
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| Genus: | Astrononion Cushman & Edwards, 1937
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The secondary chamberlets in the original description of Cushman and Edwards 1937 that give the stellate appearance were noted by Loeblich and Tappan as resulting from non-porous flaps that project backwards from each chamber partly covering the preceding suture and umbilical region but leaving a small open cavity beneath, giving the appearance of secondary chamberlets.
Astrononion has a cosmopolitan distribution and is known from the Middle Eocene to the recent. Along with Fujinonion, Laminononion, and Pacinonion, it forms the subfamily Astononioninae.
References edit
- ^ Sen Gupta 2002 Systematics of modern foraminifera in Modern Foraminifera
- N de B Hornibrook. The forminiferal genus Atrononion Cushman and Edwards. Micropaleontology Vol 10, no 3 July 1964
- Alfred R. Loeblich Jr & 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.
- A Loeblich & H Tappan, 1988. Forminiferal Genera and their Classification. e-book [1]