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Late Cretaceous nautilid beaks from near-shore/shallow water deposits of the Bohemian Cretaceous Basin (Czech Republic)

Kostak M., Vodrazka R., Frank J., Mazuch M., Marek J.

Acta Geologica Polonica

2010

Vol. 60, no. 3

417-428

More than 30 isolated nautilid jaws have been discovered in washed samples of late Cretaceous (turonian) nearshore/shallow water deposits located in the southern part of the Bohemian Cretaceous Basin (BCB). upper and lower jaws discovered in genetically-similar early turonian deposits are described in detail herein. the nautilid jaw apparatuses comprise rhyncholites (upper jaws) assigned to Nautilorhynchus simplex (Fritsch), and conchorhynchs (lower jaws) assigned to Conchorhynchus cretaceus Fritsch. some rhyncholites show signs of abrasion and corrosion, and may also form a substrate for sessile organisms. in one specimen, signs of acid digestion in the stomach of a predator were recognized. N. simplex is synonymized with "Rhyncholithus" bohemicus (till), "R". curvatus. (till), "R" rectus (till) and "R". curtus (till). the significant morphological variability observed in N. simplex is supported by biometric data. although the jaws were not found associated with body chambers, it is inferred from the extremely low nautilid biodiversity across the Cenomanian/turonian boundary interval in the BCB, and from the range and relative abundance of the only early turonian nautilid taxon present, that the jaws are probably referable to the genus Eutrephoceras hyatt and specifically to the common and long-ranging species E. sublaevigatum (d'Orbigny).

Belemnites of the Bohemian Cretaceous Basin in a global context

Kostak M., Cech S., Ekrt B., Mazuch M., Wiese F., Voigt S., Wood Christopher J.

Acta Geologica Polonica

2004

Vol. 54, no. 4

511-534

Belemnites occur infrequently from the Upper Cenomanian through the Middle/Upper Coniacian in the Bohemian Cretaceous. Four species of the family Belemnitellidae PAVLOW, 1914 have been described so far. A typical boreal faunal incursion, represented by belemnites, happened five to six times in the Bohemian Cretaceous Basin (BCB). Praeactinocamax plenus immigrated during the Late Cenomanian Metoicoceras geslinianum ammonite Zone (plenus Event); there were two short-term incursions of P. bohemicus in the Late Turonian (Subprionocyclus neptuni to Prionocyclus germari ammonite zones) and an incursion of Goniocamax lundgreni in the late Early Coniacian (below and intra-Cremnoceramus crassus inoceramid Zone). A single belemnite fragment was recorded from the "Chlomek Beds"; Middle to Upper Coniacian.Bohemian Cretaceous belemnite systematics, palaeobiogeography (including palaeobiogeographic maps reconstructed), palaeoecology (including the relationship to other coleoid groups . i. e. teuthids) and stratigraphy are discussed.