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Lower Turonian record of belemnite Praeactinocamax from NW Siberia and its palaeogeographic significance

100%

Kostak M., Wiese F.

Acta Palaeontologica Polonica

2008

tom 53

nr 4

Specimens of the belemnitellid Praeactinocamax Naidin, 1964 are described from the Upper Cretaceous of NW Siberia (Taimyr Region, Lower Agapa River, Russia). The rostra determined as Praeactinocamax aff. plenus consist of an aragonitic anterior part and a calcitic posterior part with a sharp boundary in between. This boundary surface is referred to as the “alveolar fracture”, and it is a typical morphological feature of early belemnitellids and not a result of diagenetic processes. The occurrence of Praeactinocamax in Arctic areas shows a wider palaeobiogeographical distribution of the genus in the Late Cenomanian–Early Turonian interval than previously known. This finding suggests that migration of the late Cenomanian–early Turonian fauna occurred across Turgai channel. The geographic position of these new records may also explain the occurrence of Praeactinocamax in the Turonian of the US Western Interior Seaway, the origin of which has been hitherto unclear.

Extremely rare Turonian belemnites from the Bohemian Cretaceous Basin and their palaeogeographical importance

100%

Kostak M., Wiese F.

Acta Palaeontologica Polonica

2011

tom 56

nr 2

New records of extremely rare late Turonian belemnites are described from the Úpohlavy working quarry in the Bohemian Cretaceous Basin. These specimens are referred to Praeactinocamax bohemicus (Stolley, 1916). An alveolar fragment possibly represents Praeactinocamax strehlensis (Fritsch, 1872) and would be the third find of this species ever recorded. All finds derive from a thin horizon in the uppermost part of the Hudcov limestone (Teplice Formation, uppermost Subprionocyclus neptuni Ammonite Zone). The small faunule most likely had its origin in a taxon from the Praeactinocamax manitobensis/walkeri/sternbergi group of the North American Province, and its occurrence in Europe can be seen in the context of a southward shift of Boreal taxa in the course of a late Turonian cooling event.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

2 Kostak M.

2 Wiese F.

1 2011

1 2008

Wyniki wyszukiwania

Lower Turonian record of belemnite Praeactinocamax from NW Siberia and its palaeogeographic significance

Extremely rare Turonian belemnites from the Bohemian Cretaceous Basin and their palaeogeographical importance