Amphistegina, Foraminifera,

Foraminifera by: Genus Locality Fossil

Uvigerina peregrina, Campos, Brazil, Foraminifera

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Amphistegina d'Orbigny, 1826

Type species: Amphistegina quoyi d'Orbigny, 1826 ( seen as A. radiata Fichtel and Moll by Hofker)

Description: Test: trochospiral, asymmetrically lenticular, involute with an angular, carinate periphery and lobed sutures, unequally biconvex; Chamber: numerous, with interseptal pillars, strongly curved back at the periphery (alar prolongation); Aperture a narrow slit at the inner margin of the last chamber often surrounded by pustules
Distribution: Early Eocene to recent, (according to Loeblich/Tappan 1987 since upper Cretaceous); warm, shallow water
Amphistegina lobifera Larsen, 1976 and A. lessonii d'Orbigny 1826 are widespread in the Indo-Pacific and A. gibbosa d'Orbigny, 1826 - as a sibling species to A. lessonii - in the Caribbean and West Atlantic. They live on firm substrates, both reefal and phytal and may also occur on sandy substrates at depths commonly less than 30m, A. lobifera at depth less than 10m. A. radiata Fichtel and Moll does not occur in the central Pacific. It is seen by Hofker as the type species illustrated by d'Orbigny. A. papillosa Said is flat and is the deepest living species at depth > 100m. A. bicirculata Larsen, 1976 is similar to A. lessonii, but flater
Life style: Test free, epibenthic, living in symbiosis with different symbionts (diatoms, which require blue light). The depth distribution is related to the light required by the specific symbionts. If water transparency is sufficient specimens (e.g. A. lessonii) may be found at greater depth up to 130m living together with symbionts used to little light and greater depth conditions. Due to these specific communities assemblages of calcareous algae and larger foraminifera are commonly used as proxy water-depth indicators in carbonate sediments with Amphistegina as one of its prominent representatives.
The robust tests especially of A. lobifera are adapted to a life in mobile carbonate sands and areas of increased turbidity and high hydrodynamic energy, characteristic of water depths less than 10m. Amphisteginas adjust the morphology of the apertural faces according to the needs for sticking to the substrate. They mainly live in the forereef-shelf and reef top.
Generation times are 3-12 months depending on depth and nutrition. For A. gibbosa a trimorphic life cycle is observed.
Literature: BouDagher-Fadel, M.K., 2008. Evolution and Geological Significance of Larger Benthic Foraminifera
Hallock, Pamela: Symbiont-bearing Foraminifera in Gupta, Barun K. Sen, editor (1999): Modern Foraminifera, Page 131
Hottinger, l., Halicz, E. and Reiss, Z. 1993. Recent Foraminiferida from the Gulf of Aqaba, Red Sea. Slovenska Akademija Znanosti in Umenosti (Ljubljana), classis IV, dela vol. 33
Papp, Adolf; Schmidt, Manfred E., 1985: The Fossil Foraminifera of the Tertiary Basin of Vienna, Revision of the monograph by ALCIDE d'ORBIGNY (1846), ABHANDLUNGEN DER GEOLOGISCHEN BUNDESANSTALT, Band 37, Wien

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	A. gibbosa d'Orbigny, 1826 British Virgin Islands, Carribean		A. lessonii d'Orbigny, 1826 Ala Moana, Oahu, Hawaii at beach

A. lessonii d'Orbigny, 1826 Al-Qusair, Red Sea, Egypt	A. lessonii d'Orbigny, 1826 Al-Qusair, Red Sea, Egypt	A. lessonii d'Orbigny, 1826 Al-Qusair, Red Sea, Egypt	A. lessonii d'Orbigny, 1826 Al-Qusair, Red Sea, Egypt

A. lessonii d'Orbigny, 1826 Sattahip, Thailand	A. lessonii d'Orbigny, 1826 Sattahip, Thailand	A. lessonii d'Orbigny, 1826 Sokotra/Yemen	A. lessonii d'Orbigny, 1826 Sokotra/Yemen

	A. lobifera Larsen, 1976 Ala Moana, Oahu, Hawaii	A. lobifera Larsen, 1976 Hurghada, Red Sea, Egypt

	A. radiata (Fichtel & Moll), 1798 Lankan Reef, North Male Atoll, Maldives	A. radiata (Fichtel & Moll), 1798 Lankan Reef, North Male Atoll, Maldives

	A. hauerina from Vienna-Nussdorf 1.	A. hauerina from Vienna-Nussdorf 2.

recent Neogene Paleogene Cretaceous Jurassic Triassic Permian Carboniferous Devon Silurian Ordovician