Alveolines
| Alveolines | ||||||||||||
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Alveolina oblonga from the Bavarian Helvetic Republic (thin section) |
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| Temporal occurrence | ||||||||||||
| Upper Paleocene to Upper Eocene | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Alveolina | ||||||||||||
| d'Orbigny , 1826 | ||||||||||||
In paleontology, alveolines are a group of fossil large foraminifera belonging to the genus Alveolina . They occur as rock formers in certain palaeogenic sediments . The term is sometimes used in a broader sense and then refers to all genera of the family Alveolinidae .
Systematics
Within the systematics of the foraminifera, the genus belongs to the family Alveolinidae , superfamily Alveolinaceae , order Miliolida . A polyphyletic origin is being discussed for the family Alveolinidae , which is due to a gap in the temporal occurrence of the genera assigned to it between the younger Upper Cretaceous (Upper Maastrichtian ) and the Paleocene.
distribution
The genus Alveolina is restricted to the Paleogene , with the first representatives appearing in the Paleocene , but the main distribution is in the lower to middle Eocene . From the Miocene onwards the genus Alveolinella (also recently documented) can be found ; the genus Praelveolina is older and restricted to the Upper Cretaceous. Geographically, the alveolines can be found in the area of the former Tethys Ocean , where they form important key fossils . The sites in Central Europe represent the north-western edge of their occurrence, which is reflected, among other things, in the comparative species poverty of the alveoline faunas of the Paris Basin and the Alpine Helveticum, while many more species occur in layers of the same age in the south-eastern Mediterranean and the Middle East.
morphology
The housing of the alveolines are described as spindle, cigar or zeppelin-shaped and can reach a length of up to ten centimeters. The embryonic chamber is in the center of this cylinder; the winding of the housing runs around its longitudinal axis (like a sheet of paper around a pencil). The housing chambers are further subdivided by dividing walls (septula) running in the direction of the windings, the position of which is relevant for determining the genus: In Alveolina , the septula of two adjacent chambers are “on gap”, while in all other genera of the Alveolinidae family the septula “butted” “(Distinguishable in the tangential section of the housing). The housing walls are made of high-magnesium calcite, are imperforate and, due to the secondary structure of a thick basal layer, which can ultimately fill a large part of the chamber cavity, very solid. As with many foraminifera, a generation change takes place, which is reflected in a dimorphism of the shell: Those with microspherical (small) and megalospheric (large) embryonic chambers.
Locations
Alveolins are found in Germany as fossils almost exclusively in Eocene rocks of the Helveticum on the northern edge of the Alps. Here they are - in contrast to the other large foraminifera of the Eocene (Nummulites, Assilins, Discocyclins) - comparatively rare and limited to individual layers. The reason given for this low distribution was the ecological demands of the alveolines.
literature
- Arno Hermann Müller (ed.): Textbook of palaeozoology. Volume II, part 1, 4th edition, Gustav Fischer Verlag 1993, pp. 73-74.
- Vladimir Pokorny: Basics of Zoological Micropalaeontology. Volume I, VEB Deutscher Verlag der Wissenschaften, Berlin 1958 (Reprint 1975), pp. 201–216.
- Wilfried Rönnfeld: Foraminifera. A catalog of typical shapes. 3rd edition, self-published, Tübingen 2008.
- Lukas Hottinger: About paleocaene and eocaene alveolines. In: Eclogae Geologicae Helvetiae. Volume 53, 1960, pp. 265-284.
Individual evidence
- ↑ a b Lukas Hottinger: About paleocaene and eocaene alveolines. Pp. 272-279.
- ^ Ulrich Lehmann: Paleontological Dictionary . 3. Edition. Enke, Stuttgart 1985, ISBN 3-432-83573-6 , pp. 10 .
- ↑ Vladimir Pokorny: Basics of Zoological Micropalaeontology. Pp. 267-268
- ^ Wilfried Rönnfeld: Foraminifera. A catalog of typical shapes. P. 34.
- ↑ Lukas Hottinger: About paleocaene and eocaene alveolines. P. 272.
- ↑ Herbert Hagn, Robert Darga, Rudi Schmid: Siegsdorf in Chiemgau - Earth history and primeval world . Ed .: Municipality of Siegsdorf. Siegsdorf 1992, p. 124-125 .