Goniatites

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Goniatites
Goniatites sp.  from the Devonian

Goniatites sp. from the Devonian

Temporal occurrence
Devonian to late Permian
Locations
Systematics
Multicellular animals (Metazoa)
Primordial mouths (protostomia)
Molluscs (mollusca)
Cephalopods (cephalopoda)
Ammonites (ammonoidea)
Goniatites
Scientific name
Goniatitis
Hyatt , 1884

The goniatites (Goniatitida; from the Greek γωνία = angle, corner, after the kinked sutures) are an extinct order of Young Paleozoic ammonites (Ammonoidea). During their occurrence between the Devonian and the late Permian, they make up the main part of the Ammonoidea.

Goniatites represent a number of important key fossils , especially in the Devonian and Carboniferous . Before the development of micropalaeontological methods, they were part of parastratigraphic structures in many areas, especially in marine limestone .

features

Like ammonites, goniatites have a chambered housing, which is usually wrapped in a spiral in one plane and made up of three layers. It is assumed that the housing of the animals was originally always made of calcium carbonate as aragonite . In the fossilized cases, this is often displaced by other minerals such as calcite or pyrite , or these filled a cavity in sediment that contained the previous case. The shapes of the housings vary considerably, from spherical to thin disk-shaped housings, with compact shapes predominating. The size of the case usually did not exceed 5 centimeters, and not even 15 centimeters for the largest species. The outer turns include the inner ones. Depending on the degree of the encirclement, the turns are involute - the inner turns are more or less covered by the outer turns - or evolute (the outer turns hardly enclose the inner turns). In the case of the living animal, the housing formed a series of chambers, with the living animal only sitting in the last (outermost) chamber; the chambers behind it were filled with gas or liquid. A membranous tube, called a siphon or siphunculus, connected all the chambers, it could probably serve to equalize pressure and enable the animal to ascend or descend in the water column by changing the density; it can be recognized on the fossil as a siphon cord.

In addition to the shape of the case, the attachment of the chamber partitions to the outer case - the praised line or suture - is the most important defining feature. Since the sutures correspond to the approaches of the chamber partition walls on the inside of the shell , they are only visible when the housing is removed, for example on the stone core . In contrast to the frequently puckered praise line of the ammonites, that of the goniatites is not very curved and has only gentle kinks or bends. The praise line is marked in almost all types by an adventitious lobe. The formula of praise is EALI. Almost all praises can be broken down further. A U lobe can intervene between the L and I lobes. In the early forms, the lobes are still broadly rounded, in more recent forms they are often pointed or finger-shaped. The siphon line is almost always on the ventral edge, only very rarely does the siphon line move a little away from the edge. The outside of the housing can be smooth or ornamented (ribbed). The shape of the growth lines that emerged on the outer edge as the shell grew is often of diagnostic value.

The muscular apparatus differed in details from that of the ammonites. This was the result of studies of muscle attachment sites that were preserved in pyritized goniatites. There is no evidence of a solid pine apparatus such as that which ammonites possess.

Way of life

Because of their slow swimmer lifestyle, goniatites were sea creatures close to the bottom. They settled epicontinental sea ​​areas away from the zones with strong water movement such as the surf zones. According to paleogeographic reconstructions, their habitats can be described as subtropical to tropical . Little is known about the diet of the goniatites.

Occurrence

Goniatites are common in Devonian and Carboniferous limestone and claystones . Areas with frequent goniatites are for example:

Systematics

The order is currently divided into two sub-orders, each with numerous superfamilies:

literature

  • Thomas Becker, Jürgen Kullmann: Paleozoic Ammonoids in Space and Time. In: Neil L. Landman, Kazushige Tanabe, Richard Arnold Davis (eds.): Ammonoid Paleobiology (= Topics in Geobiology. Vol. 13). Plenum Press, New York NY et al. 1996, ISBN 0-306-45222-7 , pp. 711-753.
  • Dieter Korn , Christian Klug: Ammoneae Devonicae (= Fossilium Catalogus. 1: Animalia. Ps. 138). Backhuys Publishers, Leiden 2002, ISBN 90-5782-119-2 .
  • Emil Kuhn-Schnyder , Hans Rieber: Paleozoology. Morphology and systematics of extinct animals. Georg Thieme, Stuttgart et al. 1984, ISBN 3-13-653301-1 .
  • Anthea Lacchia (2012): Goniatites. Fossils explained 64. Geology Today Vol. 28, No. 5: 192-196. doi : 10.1111 / j.1365-2451.2012.00851.x

Web links

Commons : Goniatites ( Goniatitida )  - Collection of images, videos and audio files

Individual evidence

  1. Ute Richter: Tissue attachment structures on pyritized stone cores of ammonoids (= Geological Contributions Hanover. Vol. 4, ISSN  1615-6684 ). Institute for Geology and Paleontology, Hannover 2002 (Simultaneously: Hannover, Universität, Dissertation, 2002; short version  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove it Note. ).@1@ 2Template: Toter Link / www.user.uni-hannover.de