Arietites

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Arietites
Arietites

Arietites

Temporal occurrence
Lower Sinemurium
199.3 to 197.8 million years
Locations
Systematics
Cephalopods (cephalopoda)
Ammonites (ammonoidea)
Ammonitida
Arietitidae
Arietitinae
Arietites
Scientific name
Arietites
Scales , 1869

Arietites is a genus of giant evolutionary ammonites . It occursworldwidein the Lower Sinemurium .

Taxonomy

Arietites bucklandi from Balingen

The genus Arietites belongs to the family of the Arietitidae (subfamily Arietitinae ) within the superfamily of the Psiloceratoidea . It contains the following taxa:

Note: Arietites today only represents a purely morphological term - devoid of any phylogenetic classification. A revision of the genus is still pending , its representatives are therefore classified as Coroniceras (Arietites) under Coroniceras for the time being .

phylogenesis

The superfamily of the Arietitoidea (or Arietitaceae ) had developed from the superfamily of the Psiloceratoidea at the beginning of the Oberhettangiums 199.7 million years ago . The superfamily Hildoceratoidea (with the genus Hildoceras ) emerged from it at the beginning of the Pliensbachian period 189.6 million years ago .

description

Taxa of the genus Arietites become very large, sometimes huge. Arietites bucklandi can develop giant shapes over 80 centimeters in diameter. The flat or only slightly bulged flanks of the animals are coarse transversely and relatively broadly ribbed, the straight to slightly curved, rather thick ribs, however, are lost on the inside of the housing windings. The ribs can have small tubercles on the ventral side. On the flattened or slightly convex venter runs a not too high, narrow, rounded keel, which is accompanied by a longitudinal pair of furrows ( sulci ). The shape of the rounded winding cross-section is rectangular to almost square (with a width / height ratio of 0.9). The line of praise is only moderately grooved. The first lob saddle is at the same height as the outer saddle and can also protrude slightly above it. The external lobe is furrowed deepest.

Ammonite zone

The taxon Arietites bucklandi or Coroniceras bucklandi forms the first ammonite zone of the Sinemurian - the Bucklandi zone - and defines the beginning of the stage . It follows over the Angulata zone of the Hettangium named after Schlotheimia angulata . The semicostatum zone of the lower Sinemurium, named after Arnioceras semicostatum , lies over them .

The Bucklandi zone consists of three subzones, the Conybeari subzone named after Metophioceras conybeari , the overlying rotiform subzone named after Coroniceras rotiforme and the Bucklandi subzone named after Arietites bucklandi . The Conybeari subzone is further subdivided into three biozones - Latisulcatum in the horizontal , above Rotarium and Conybeari in the hanging wall . The Latisulcatum biozone consists of three horizons - Vermiceras quantoxiense , above Metophioceras sp. 2 and Metophioceras conybearoides .

The change of fauna from the genus Schlotheimia to the genera Vermiceras and Metophioceras defines the GSSP of the Sinemurian in Somerset .

The Rotarium Biozone is made up of four horizons - Epammonites rotarius in the horizontal position, followed by Metophioceras rouvillei , Coroniceras rotator and Vermiceras elegans in the hanging wall . The Conybeari biozone consists only of the Metophioceras conybeari horizon .

The rotiform subzone is made up of the two biozones Hyatti in the recumbent and Schloenbachi in the hanging wall. The Hyatti biozone is divided into the five horizons Epammonites silvestrei lying down, followed by Coroniceras cf. defneri , Coroniceras rotiforme , Coroniceras aff. rotiforme and Coroniceras caprotinum in the hanging wall . The Schloenbachi biozone consists only of the Coroniceras kridion horizon .

Finally, the Bucklandi subzone has the three biozones coronaries in the lying wall, followed by Isis and Bisulcatus in the hanging wall. The coronaries biozone only has the Vermiceras scylla horizon . The Isis biozone consists of the three horizons Arietites aff. isis , Arietites isis and Arietites aff. scunthorpense . The final Bisulcatus biozone contains only the Coroniceras multicostatum horizon .

Way of life

The individuals of Arietites were fast swimming marine carnivores that lived primarily in the deep subtidal and on the shelf slopes .

Ariete layers and ariete lime

Arieten pavement in the Steinlach near Ofterdingen

The ariet layers in Northern Germany and the Arietenkalk of the southern Jura were named after the genus Arietites . In this context, the so-called snail pavement made of ariet limestone in the Steinlach stream bed in Ofterdingen is worth seeing .

Occurrence

Arietites' sites in Germany are Aldingen , Balingen ( Endingen and Engstlatt ), Blumberg , Bodelshausen , Kirchheim unter Teck , Ofterdingen , Rheinfelden (Adelhausen), Sankt Georgen , Stuttgart-Degerloch , Trossingen and Vaihingen an der Enz in Baden-Württemberg , Bündheim , Cremlingen and Rottorf am Klei in Lower Saxony , Bielefeld in North Rhine-Westphalia , Hötensleben in Saxony-Anhalt and the seamounts near Gotha in Thuringia .

In Austria , Lorüns in Vorarlberg should be mentioned, in Switzerland Frick in the canton of Aargau . In France , the genus Arietites appears in the western Alps in the Oisans (in the basin of Le Bourg-d'Oisans ). In Albania the genus Arietites was found near Shkodra and in Greece in Crete in the Talea Ori .

Outside of Europe, the genus Arietites appears in Turkey at Köserelik-Kizik ( Tokat Province ) and in Indonesia on Timor .

Photo gallery

  • Arieten plaster from Bodelshausen

  • Arietites brookei - Lyme Regis

  • Arietites bucklandi from Hötensleben

  • Arietites bucklandi from Ofterdingen

  • Arietites obtusus from Bündheim (Bad Harzburg)

literature

  • WJ Arkell et al .: Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology. Geological Society of America and University of Kansas Press, 1957.

Individual evidence

  1. ↑ JJ Sepkoski: A compendium of fossil marine animal genera . In: Bulletins of American Paleontology . tape 363 , 2002, p. 1-560 .
  2. ^ Jean Guex, David Taylor, Milos Rakus and Hugo Bucher: New data on the phylogeny of Liassic Ammonites . In: Bull. Soc. vaud. Se. nat. tape 87.2 , 2000, pp. 109-114 .
  3. ^ Gert Bloos and Kevin N. Page: Global stratotype section and point for base of Sinemurian Stage (Lower Jurassic) . In: Episodes . tape 25 , 2002, pp. 22-28 .
  4. ↑ Kevin N. Page: The Lower Jurassic of Europe: its subdivision and correlation . In: Geological Survey of Denmark and Greenland Bulletin . tape 1 , 2003, p. 23-59 .
  5. ↑ M. Gruner: Dynamic paleoecology and taxonomic treatment of the Lower Jurassic (Hettangian to Lower Sinemurian) on the Swabian Alb . In: Profile . tape 11 . Stuttgart 1997, p. 1-197 .