Harpoceras

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Harpoceras
Harpoceras subplanatum from the Isère department

Harpoceras subplanatum from the Isère department

Temporal occurrence
Toarcium
182.0 to 150.8 million years
Locations
Systematics
Primordial mouths (protostomia)
Molluscs (molluscum)
Cephalopods (cephalopoda)
Ammonites (ammonoidea)
Hildoceratidae
Harpoceras
Scientific name
Harpoceras
Scales , 1869

Harpoceras is a genus from the extinct group of ammonites characterized by sometimes quite large, only moderately developed (evolute) housing. It is to be assigned to the Toarcium , a chronostratigraphic level of the Lower Jurassic , and isthe second key fossil of this levelafter the genus Dactylioceras .

description

In the size of their phragmocone , members of the genus Harpoceras show a clear dimorphism . The microconch diameters are between 24 and 31 millimeters, whereas macroconches reach diameters from 115 to 430 millimeters. In addition to their size, micro and macro conches differ in the design of the navel. The umbilical edge of micro-conches is rounded, but of macro-conches it tapers to a point. The umbilical wall is convex in microconches, oblique to undercut in macroconches.

The somewhat flattened housing can be slightly involute to slightly evolved (N = U / D = 0.23 to 0.30, maximum up to 0.46). The winding cross-section is flattened longitudinally oval with an accentuated hollow keel. The strong but not very high ribs are crescent-shaped with a concave opening pointing forward. In the outer turns, the ribs can also be wide and flattened and are occasionally grooved lengthways in the inner turns. On some taxa there is a groove or undulating depressions in the middle. The praise lines are deeply grooved and richly decorated with a characteristic outer saddle and a very developed auxiliary globe.

Way of life

The genus Harpoceras lived as a free-swimming necton and stayed mainly in limestone-depositing shelf seas off the coast in the shallow to deeper subtidal , but was also found above the shelf ramps and underwater fans.

Systematics

Harpoceras serpentinum

The genus Harpoceras forms part of the family of Hildoceratidae and the subfamily Harpoceratinae Neumayr , 1875. From her following taxa are known:

The type species is Ammonites falcifer Sowerby , 1820.

Sub-genera are:

Cleviceras , Eleganticeras , Osperleioceras , Ovaticeras , Polyplectus , Pseudolioceras , Sphenarpites , Taffertia and Tiltoniceras act as sister taxa .

To be handled synonymously:

  • Falcifericeras Breistroffer , 1949
  • Gallitellia Venturi and Ferri , 2001
  • Glyptarpites Buckman , 1927
  • Harpoceratoides Buckman , 1909
  • Kolymoceras Dagis , 1970
  • Lioceras Bayle , 1878
  • Maconiceras Buckman , 1926
  • Phaularpites Buckman , 1928
  • Tardarpoceras Buckman , 1927

Ammonite zones

Harpoceras (Eleganticeras) elegans

The genus Harpoceras is a key fossil in the Serpentinum Zone , named after Harpoceras (Harpoceras) serpentinum . The Serpentinum Zone is the second ammonite zone of the Toarcium and follows the Tenuicostatum Zone . It is overlaid by the Bifrons zone .

Internally, it is divided into the Exaratum subzone (according to Cleviceras exaratum ) in the horizontal and the Falciferum subzone (according to Harpoceras (Harpoceras) falciferum ) in the hanging wall .

The Exaratum subzone consists of three biozones, the horizon of Elegantuliceras elegantulum at the base, above the horizon of Cleviceras exaratum and the horizon of Cleviceras elegans in the top. In the Sub-Mediterranean Fauna Province, the last two horizons are replaced by the horizon of Harpoceras (Harpoceras) strangewaysi .

The Falciferum subzone is divided into two horizons, the horizon of Harpoceras (Harpoceras) pseudoserpentinum in the lying wall and the horizon of Harpoceras (Harpoceras) falciferum in the hanging wall. The latter is exchanged for the horizon of Orthildaites douvillei in the Submedterranen Province .

Occurrence

Harpoceras capillatum

Occurrences of the genus Harpoceras in Germany are Achalm , Bad Schönborn near Karlsruhe , Dotternhausen , Eningen , Holzmaden and Reutlingen - all in Baden-Württemberg . Bavarian sites are Lauf an der Pegnitz , Wassertrüdingen and Westheim in Middle Franconia , Eggolsheim (Unterstürmig) in Upper Franconia and Freudenberg in Upper Palatinate . Also worth mentioning are Cremlingen , the Haverlahwiese and Vehre pit in Lower Saxony and gravel pits in the Stormarn district in Schleswig-Holstein .

The Northwest European Fauna Province also includes the English finds near Whitby in Yorkshire and occurrences in Switzerland , near Belvaux in Luxembourg and France .

The French sources are very numerous, Harpoceras appears, for example, in the Causses near Saint-Jean-et-Saint-Paul ( Département Aveyron ), in the Corbières near Bizanet , Aguilar , Feuilla , Fitou , Fontjoncouse , Fraissé-des-Corbières and Treilles ( Aude department ), in the Pyrenees , in the department of Ardennes in Charleville-Mezieres , in the Charente in Roumazières-Loubert , in Deux-Sevres in Airvault , Mauzé-Thouarsais , Saint-Maixent-l'Ecole , Sainte-Verge in Thouars ( Type locality des Toarciums) and Thorigné , in the Isère department , in the Pyrénées-Orientales department near Calce and on Grau de Maury , in the Rhône department near Lyon , in the Seine-Maritime department near Bléville , in the Tarn-et-Garonne near Caylus , in the department Vendée near Bessay , Chantonnay , Jard-sur-Mer , Le Bernard , Moutiers-sur-le-Lay , Péault , Pissotte , Saint-Hilaire-la-Forêt and Saint-Martin-des-Fontaines and in the Vienne department near Champagné-Saint -Hilaire , Ligugé and Queaux .

The Mediterranean fauna province of the Tethys area includes the sites in Spain , Italy , Hungary , Bulgaria , Albania , the Caucasus as well as Morocco , Tunisia and Indonesia , whereas Japan and New Zealand are already included in the Pacific area.

In addition, Harpoceras appears in Somalia , in East Africa's Indian-Malagasy Fauna Province, as well as in Canada in North America and also near Mendoza in Argentina in South America .

literature

  • MK Howarth: The Ammonite family Hildoceratidae in the Lower Jurassic of Britain . In: Monograph of the Palaeontographical Society - The Palaeontographical Society . London 1992, p. 109 .
  • Pierre Lacroix: Les Hildoceratidae du Lias moyen et supérieur des domaines NW européen et téthysien - Une histoire de famille . 2011, p. 90 .

Individual evidence

  1. ^ Paleobiology Database , accessed September 21, 2012
  2. ↑ Sepkoski's Online Genus Database , accessed September 21, 2014
  3. ↑ Lexicon of Biology: Ammonoidea. Retrieved September 21, 2014 .
  4. ^ S. Guérin-Franiatte, R. Maquil and P. Münzberger: Le Toarcien au Grand-Duché de Luxembourg: Biostratigraphie dans la région de Belvaux . In: Le Jurassique inférieur et moyen au Luxembourg - Ferranti . tape 62 . Travaux scientifiques du Musée d'Histoire Naturelle du Luxembourg, 2010, p. 19-34 .
  5. ↑ R. Jattiot and V. Trincal: Guide of ammonites pyriteuses. Toarcien moyen et supérieur des Causses (Lozère - France) . Les Editions du Piat, 2015, p. 55 .
  6. ^ P. Fauré: Le Lias des Pyrénées - doctoral thesis . In: STRATA - Series II . Vol. 39. Laboratoire de Géologie sédimentaire et Paléontologie, Université Paul-Sabatier, Toulouse, France 2002, p. 718 .
  7. ↑ J. Gabilly: Le toarcien à Thouars et dans le center-ouest de la France . CNRS, 1976, p. 104 .
  8. ↑ M. Bécaud: Les Harpoceratinae, Hildoceratinae et Paroniceratinae du Toarcien de la Vendée et des Deux-Sèvres (France) . In: Documents des Laboratoires de Géologie de Lyon . No 162. UFR des Sciences de la Terre - Université Claude Bernard - Lyon I, 2006, p. 65 .
  9. ^ GR Stevens: The ammonite genus Harpoceras (Early Jurassic) in New Zealand . In: New Zealand Journal of Geology and Geophysics . Vol. 50, Issue 4, 2007, pp. 377-386 , doi : 10.1080 / 00288300709509845 .

Web links

Commons : Harpoceras  - collection of images, videos and audio files