Tragophylloceras

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Tragophylloceras
Tragophylloceras numismale (second specimen top left) and mainly Androgynoceras lataecosta

Tragophylloceras numismale (second specimen top left) and mainly Androgynoceras lataecosta

Temporal occurrence
Pliensbachium
189 to 185 million years
Locations
Systematics
Cephalopods (cephalopoda)
Ammonites (ammonoidea)
Ammonitida
Phylloceratoidea
Juraphyllitidae
Tragophylloceras
Scientific name
Tragophylloceras
Hyatt , 1900

Tragophylloceras is a genus of involute, only indistinctly ribbed ammonites . It occursquite widely as a key fossil of the Ibex zone in the lower Pliensbachian ( Carixian ).

Initial description and naming

The genus Tragophylloceras was first described by Alpheus Hyatt in 1900 . Its name is a word created from the three Greek words τράγος tragos (billy goat), φύλλον phyllon (leaf) and κέρας keras (horn), where phyllon refers to the leaf-shaped shape of the praise line and keras to the curling in the form of ram's horns.

characterization

The genus Tragophylloceras consists of quite small forms that rarely exceed 10 centimeters. Since the genus shows dimorphism , however, macroforms can reach up to 22 centimeters (e.g. in Tragophylloceras numismale ). As a typical representative of the phylloceratoidea it has an open umbilicus. Their phragmocone is involute with N = 0.13-0.22. The growth lines are sigmoid. The ribs are usually very indistinct and can even be absent entirely. It can be seen in particular as low lines of folds on the vent, it is only roughly indicated on the living chamber. The winding cross-section is compressed with parallel sides, slightly triangular at the venter and overall ogival shape (subogival). The line of praise is phylogenetically significant and consists of two distinct saddles S1 and S2, but adult forms show a total of six to seven saddles. The saddles are frayed like a leaf, the first saddle being monophyllic and the following saddles as good as diphyllic.

Tragophylloceras is one of the rare ammonite genera with well-preserved color drawings. So has Tragophylloceras loscombi similar Amaltheus spinatum longitudinal streaks.

Systematics

The genus Tragophylloceras belongs to the family of Juraphyllitidae Arkell , 1950 within the superfamily of Phylloceratoidea . The following taxa are known from her:

Tragophylloceras robinsoni is very likely a synonym of Tragophylloceras loscombi . Tragophylloceras huntoni and Tragophylloceras nanus are synonyms of Tragophylloceras numismale , Tragophylloceras radstockense and Tragophylloceras Wechsleri from Tragophylloceras undulatum .

Fergusonites , Juraphyllites , Nevadaphyllites , Paradasyceras and Togaticeras act as sister taxa .

The genetic assignment to the Juraphyllitidae is based on very similar characteristics, because Tragophylloceras differs from the Phylloceratidae due to the open umbilicus and the ornamented outer convolutions. Based on purely morphological considerations, it can be assumed that the genus developed either from Juraphyllites or from the Hettangian subfamily Calliphylloceratinae of the Phylloceratoidea.

Way of life

The individuals of the genus Tragophylloceras were marine carnivores that populated the shallow as well as the deeper calcareous subtidal far away from the coast and followed drifting plankton .

Ammonite zone

The genus Tragophylloceras is a key fossil and defines the second ammonite zone of the Pliensbachian, the Ibex zone . The Ibex zone follows the Jamesoni zone and is in turn overlaid by the Davoei zone .

The Ibex zone, named after Tragophylloceras ibex , is made up of three subzones, the Masseanum subzone in the lying wall, followed by the Valdani subzone and the Luridum subzone in the hanging wall . The masseanum subzone, named after Tropidoceras masseanum , consists only of the masseanum biozone. The Valdani subzone, named after Acanthopleuroceras valdani , contains five biozones, the Arietiforme biozone lying down, above that the Maugenesti biozone, the Valdani biozone, the Actaeon biozone and finally the Alisiense biozone. The Luridum subzone, named after Beaniceras luridum , is in turn made up of three biozones, the rotundum biozone in the lying position, the crassum biozone and the Luridum biozone in the top.

Tragophylloceras numismale already appears in the Jamesoni zone (Taylori and Polymorphus subzones). In the Ibex zone, Tragophylloceras undulatum (entire Ibex zone), Tragophylloceras ibex (only Valdani subzone) and Tragophylloceras carinatum (Valdani and Luridum subzone) are added. Tragophylloceras loscombi only appears towards the end of the Ibex zone, survives the entire Davoei zone and only disappears towards the end of the Margaritatus zone. It is difficult to verify whether Tragophylloceras undulatum and Tragophylloceras ibex developed from Tragophylloceras numismale , but Tragophylloceras carinatum may have emerged from Tragophylloceras undulatum , as may also Tragophylloceras loscombi .

Occurrence

Sites of the genus Tragophylloceras in Germany are next to the Swabian Alb (for example, in Ofterdingen , Pliensbach and Reutlingen ) in Baden-Wuerttemberg Ehenfeld in Hirschau in Bavaria , the region of Bonenburg at Warburg and Herford in North Rhine-Westphalia and Beierstedt , Gebhardshagen and Wohld in Lower Saxony .

There are numerous sites in France , for example in the Calvados department ( Fresnay-le-Puceux , Basse-Normandie), in the Cher department and in the Carixium der Causses near Rivière-sur-Tarn and Saint-Georges-de-Luzençon .

Find sites in the United Kingdom are the Charmouth Mudstone Formation in Dorset , Blockley , Cheltenham and Leckhampton in Gloucestershire , Old Dalby in Leicestershire , Mull , Collin Glen and Portrush in Northern Ireland , Barby , Kilsby and Watford in Northamptonshire , Pabay ( Skye ), Paulton and Radstock in Somerset as well as Northcliff , Robin Hood's Bay and Whitby in Yorkshire .

Outside Europe, the genus Tragophylloceras appears on Musandam in the Ghalilah Formation of the United Arab Emirates and in the Fannin Formation on the Queen Charlotte Islands in Canada .

literature

  • William Joscelyn Arkell et al .: Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology. Geological Society of America and University of Kansas Press, 1957.
  • Raymond Cecil Moore : Treatise on Invertebrate Paleontology . Part L. Mollusca 4. Ammonoidea. Geological Society of America, 1957, pp. 248 .
  • 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. ↑ Jack Sepkoski : A compendium of fossil marine animal genera . In: Bulletins of American Paleontology . tape 363 , 2002, p. 1-560 .
  2. ↑ Otto Heinrich Schindewolf : Again about colored stripes in Amaltheus (Paltopleuroceras) spinatum (Brug.) . In: Paleont. Time. tape 13 , 1931, p. 284-287 .
  3. ^ MK Howarth and DT Donovan: Ammonites of the Liassic family Juraphyllitidae in Britain . In: Palaeontology . Vol 7, Part 2, 1964, pp. 286-305 .
  4. ↑ Jean-Luc Dommergues et al .: Les ammonites du Pliensbachien et du Toarcien basal dans la carrière de la Roche Blain (Fresnay-le-Puceux, Calvados, Basse-Normandie, France). Taxonomy, implications stratigraphiques et paleobiogéographiques . In: Revue de Paléobiologie . Muséum d'Histoire Naturelle de la ville de Genève 2008, p. 277 .
  5. ^ Christian Meister: Les ammonites du Carixien des Causses (France) . In: Swiss palaeontological treatises . tape 109 , 1986, pp. 1-209 .
  6. ^ WD Lang, LF Spath, LR Cox and HM Muir-Wood: The Belemnite marls of Charmouth, a series in the Lias of the Dorset Coast . In: Quarterly Journal of the Geological Society . tape 84 , 1928, pp. 179-257 .
  7. ^ MHM Metwally and MSM Ali: The Triassic-Jurassic boundary in the Elphinstone Group, western part of the Musandam Peninsula, United Arab Emirates . In: New Yearbook for Geology and Paleontology, monthly books . tape (5) , 1992, p. 257-266 .
  8. ^ PL Smith and HW Tipper: Pliensbachian (Lower Jurassic) ammonites of the Queen Charlotte Islands, British Columbia . In: Bulletins of American Paleontology . tape 108 (348) , 1996, pp. 1-122 .