Acta Palaeontologica Polonica

Note on some Cranias from central Poland

Alfred Rosenkrantz

Acta Palaeontologica Polonica 09 (4), 1964: 513-531

Two kinds of Cranias have been collected between 193 m. and 207 m. in a boring at Boryszew, central Poland. Most valves represent a new member of the "Crania tuberculata group". For members of this group, comprising species from the Maastrichtian, Danian, Paleocene and ?Eocene, a new subgenus of Crania - C. (Danocrania) n.subg. is erected with Crania tuberculata Nilsson as type species. The Polish representatives are named: C. (Danocrania) polonica n.sp. and C. (Danocrania) polonica semicostulata n.subsp. The subspecies shows a peculiar outer sculpture very similar to that shown by a C. (Danocrania) from the upper Middle Danian of Faxe (Denmark). The remaining Cranias all belong to the subgenus C. (Isocrania), known only in association with C. (Danocrania) in Danian strata. The Polish form is related to C. (Isocrania) posselti Rkz. from the Upper Danian of Denmark. The age of the Crania-bearing strata at Boryszew is estimated to be upper Middle Danian. If the strata are younger, their Danian fossil content, e.g. the Cranias, Tylocidaris masoviensis Kongiel and Stereocidaris rosenkrantzi (Ravn), must be considered as derived fossils. A ventral valve of the Upper Senonian C. (Isocrania) paucicostata Bosquet in Lower Paleocene strata at Bochotnica shows that derived fossils may occur in the Lower Paleocene of central Poland.

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