Echioceras

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Echioceras
Echioceras raricostatum

Echioceras raricostatum

Temporal occurrence
Sinemurium
196.5 to 189.6 million years
Locations
Systematics
Cephalopods (cephalopoda)
Ammonites (ammonoidea)
Ammonitida
Psiloceratoidea
Echioceratidae
Echioceras
Scientific name
Echioceras
Bayle , 1878

Echioceras is a genus of small, evolutionary, ribbed ammonites . It occursquite widespreadas a key fossil in the upper Sinemurian ( Lotharingian ).

description

The narrow and flattened phragmocones of the genus Echioceras are on average not much larger than 4 to 6 centimeters. With a ratio N = umbilical width U / total width D of 0.6, they are to be classified as evolutionary shapes. The inner turns are reinforced by slender ribs, which, however, progressively develop a more and more distinctive and straightforward appearance towards the outer turns. The density of the ribs decreases rapidly in the course of ontogenetic development. The winding cross-section is almost circular. The center of the vent has an indistinct keel without a sulci. The ribs are perpendicular to the keel - a key feature of Echioceras .

Way of life

The individuals of the genus Echioceras were fast- swimming , marine carnivores that populated the shallow calciferous Subtidal away from the coast .

Systematics

The genus Echioceras belongs to the family of the Echioceratidae (subfamily Echioceratinae ) within the superfamily of the Psiloceratoidea . The following taxa are known from her:

Gagaticeras , Leptechioceras , Orthechioceras , Palaeoechioceras , Paltechioceras and Plesechioceras act as sister taxa .

Ammonite zone

The genus Echioceras is a key fossil in the Raricostatum zone (ammonite zone named after Echioceras raricostatum ), the last ammonite zone of the Sinemurian. It occurs here in the basal densinodulum subzone as well as in the overlying Raricostatum subzone.

In the Densinodulum subzone the genre appears Echioceras until the Radiatum-Biozone in the hanging wall . The Radiatum biozone is divided into two horizons (horizons XXVIII to XXIX of the Lotharingium), the horizon of Echioceras radiatum at the base and the horizon of Echioceras sp. 3 in the top.

In the Raricostatum subzone, the genus Echioceras occurs in the lowest three of a total of four biozones (horizons XXX to XXXII of the Lotharingium), namely in the basal Rhodanicum biozone with the horizon of Echioceras rhodanicum followed by the Raricostatum biozone with the horizon of Echioceras raricostatum and finally in the Crossicostatum biozone with the horizon of Echioceras crossicostatum .

In the Tethyalen area of the Alps, the horizon of Echioceras rhodanicum is replaced by the horizon of Echioceras quenstedti . The horizon of Echioceras raricostatum above it is replaced by the horizon of Echioceras raricostatoides . The horizon of Echioceras crossicostatum is missing.

Occurrence

As occurrences of the genus Echioceras in Germany , Aldingen in Baden-Württemberg , Rottorf am Klei in Lower Saxony , Bonenburg near Warburg and the area around Herford in North Rhine-Westphalia are to be cited. It also appears on the seamounts near Gotha in Thuringia . Find sites in Austria are on the Walled-in and on the Formaletsch north of Dalaas and near Schröcken in Vorarlberg .

In England , Echioceras is published by Radstock in Somerset and Charmouth in Dorset . Find sites in Northern Ireland are Collin Glen and Portrush . Couches and Pierreclos in the Saône-et-Loire department are to be cited as sites in France .

Occurrences of the genus Echioceras outside Europe are found in the Murray Ridge Formation in the Northwest Territories and in the Almstrom Creek Formation in the northern Yukon in Canada .

literature

  • WJ Arkell et al .: Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology. Geological Society of America and University of Kansas Press, 1957.
  • 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 .
  • Rudolf Schlegelmilch: The ammonites of the southern German Lias: an identification book for fossil collectors and geologists. - 2nd edition Gustav Fischer Verlag, Stuttgart, Jena, New York 1992, p. 241 .

Individual evidence

  1. ↑ JJ Sepkoski: A compendium of fossil marine animal genera . In: Bulletins of American Paleontology . tape 363 , 2002, p. 1-560 .
  2. ↑ Kevin N. Page: The sequence of ammonite correlated horizons in the British Sinemurian (Lower Jurassic) . In: Newsletters on Stratigraphy . tape 27 , 1992, pp. 129-15 .
  3. ↑ 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 .
  4. ↑ Joachim Blau, Christian Meister, Rainer Ebel and Rudolf Schlatter: Upper Sinemurian and Lower Pliensbachian ammonie faunas from Herford-Diebrock area (NW Germany)) . In: Paleontological Journal . tape 74 (3)) , 2000, pp. 259-280 .
  5. ^ Christian Meister and J. Georg Friebe: Austroalpine Liassic Ammonites from Vorarlberg (Austria, Northern Calcareous Alps) . In: Contribution. Paläont. tape 28 . Vienna 2003, p. 9-99 .
  6. ↑ M. Edmunds, M. Varah and A. Bentley: The ammonite biostratigraphy of the Lower Lias "Armatum Bed" (Upper Sinemurian-Lower Pliensbachian) at St Peter's Field, Radstock, Somerset . In: Proceedings of the Geologists' Association . tape 114 (1) , 2003, pp. 65-96 .
  7. ↑ TP Poulton: Hettangian through Aalenian (Jurassic) guide fossils and biostratigraphy, Northern Yukon and adjacent Northwest Territories . In: Geological Survey of Canada Bulletin . tape 410 , 1991, pp. 1-95 .