Globigerinida

Globigerinida is an order bearing housing from the group of single-celled foraminifera. An outdated German term is over animals. She is the only order of foraminifera, whose species live plankton.

Features

Almost all species of the order form housing made ​​of calcite, which in all extant species have a very low magnesium content have (low -magnesium calcite ), only with some fossil species and high -magnesium calcite (> 5 mol% Mg ) is proved. An exception is the case of fossil Favusellacea, which consisted of aragonite. The wall of the housing is interspersed with numerous pores that are significantly greater than in benthic species living and built bilamellar, that is the cell substance is found between an inner and an outer wall. The almost circular in elevation chambers of Kalkgehäuses are spirally ( trochospiral, planispiral ) or arranged in rows.

In addition to the Miliolida and Rotaliida the Globigerinida are one of three foraminiferal orders that serve as hosts for photosynthesizing endosymbionts. Such symbioses are in the planktonic and thus lichtnah living Globigerinida However, unlike other systems, the rule. The endosymbionts are dinoflagellates or Golden-brown algae.

Paleontology

Globigerinida are an important component of the zooplankton world. Your body sink to her death down, accumulate on the sea floor, where they form one of the most common marine sediments, the so-called " Globigerina ooze ". In the course of geological processes form as sediments that are in paleontology to stratigraphic analysis is of great importance. Due to the extremely frequent finds its evolution is extremely well researched since the Miocene.

All seven extant families are fossil evidence since the Miocene, the Guembelitriidae since the Cretaceous. Your evolutionary origin, however, is not adequately known, maybe they went in front of around 180 million years emerge from the Oberhauserellidae.

System

The order includes three superfamilies tart with seven families:

• Superfamily Heterohelicacea Guembelitriidae
• Chiloguembelinidae

• Globorotaliidae
• Pulleniatinidae
• Candeinidae

• Globigerinidae
• Hastigerinidae

Both their position within the foraminifera as well as the internal classification of Globigerinida based on purely morphological features. First molecular genetic studies based on rRNA resulted in little meaningful results, since the exchange rate non-coding bases at Globigerinida around fifty to one hundred times as high as in benthic foraminifera, but indicated a close proximity to the Rotaliida. Subsequent phylogenetic analyzes based on actin confirmed this, there were found the Globeriginida as a sister taxon Rotaliida, indicating that the Globigerinida are part of the Rotaliida. For a final classification but it requires further investigation.

Mineral

Globigerinenkalk is mined in Malta as ocher-colored limestone. Typical houses are being built on this island from this building material and appear yellowish.

Evidence

• Barun K. Sen Gupta: Systematics of modern Foraminifera, In: Barun K. Sen Gupta (ed. ): Modern Foraminifera. Springer Netherlands ( Kluwer Academic ), 2002, ISBN 978-1-4020-0598-5, pp. 32-33.