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1
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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
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2008
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tom 53
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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.
2

Belemnites from the Szlachtowa Formation [Middle Jurassic], Pieniny Klippen Belt, Carpathians

100%
Krawczyk A. J., Krobicki M., Slomka T.
Bulletin of the Polish Academy of Sciences. Earth Sciences
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1992
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tom 40
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nr 1
3
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Cephalopods (Mollusca: Cephalopoda) in the palaeontological collection of the Faculty of Biology, Adam Mickiewicz University

80%
Konwerski S., Bloszyk J.
Folia Malacologica
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2012
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tom 20
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nr 1
4
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Extremely rare Turonian belemnites from the Bohemian Cretaceous Basin and their palaeogeographical importance

80%
Kostak M., Wiese F.
Acta Palaeontologica Polonica
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2011
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tom 56
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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.
5
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Fusiteuthis polonica, a rare and unusual belemnite from the Maastrichtian

80%
Christensen W. K.
Acta Palaeontologica Polonica
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2002
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tom 47
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nr 4
A specimen of Fusiteuthis polonica, from the basal Maastrichtian of the “Saturn” chalk pit at Kronsmoor in northwest Germany, is described. It came from the uppermost part of the Belemnella lanceolata Zone, ca. 9.5 m above the base of the Maastrichtian as defined on belemnites. Fusiteuthis was very rare, but widely distributed. Single occurrences are known from northwest Germany, Poland and Crimea. It has been recorded only from the lowest and uppermost parts of the Maastrichtian; the longevity of this genus was thus slightly less than 6 myr. Fusiteuthis belongs to the Upper Cretaceous belemnite family Belemnitellidae.
6
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Aragonitic rostra of the Turonian belemnitid Goniacamax: arguments from diagenesis

70%
Dauphin Y., Williams C. T., Barskov I. S.
Acta Palaeontologica Polonica
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2007
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tom 52
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nr 1
The hypothesis that belemnitid rostra are formed by primary biogenic low−Mg calcite is widespread. However, the coexistence in the same rostrum of both aragonitic and calcitic components has been reported in true belemnites (Goniocamax, Turonian). A combined microstructural and chemical composition study of the comparison of shells with undisputed mineralogy from the same site as the Turonian Goniocamax, shows that these aragonitic shells display the effects of diagenetic alteration. These observations favour the hypothesis that belemnite rostra are composed of primary aragonite, rather than low−Mg calcite, and are consistent with all other cephalopod shells. Calcitic and aragonitic rostra are also known in other Dibranchiata such as Triassic Aulacocerida and Eocene Belopterina. Diagenetic changes such as shown here may clearly affect palaeo−environmental interpretations based on carbonate shells.
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