Small brachiopods of the families Craniidae Menke, 1828 and Thecidellinidae Elliott, 1958 were selected from the Oxfordian sequence which lies transgressively upon a Variscan rhyodacite laccolite exposed at Zalas in the Cracow Upland, southern Poland, a site which is well-known due to various kinds of ubiquitous fossils. The craniids include three species: Craniscus bipartitus (Münster in Goldfuss, 1837), Craniscus tripartitus (Münster in Goldfuss, 1837) and Craniscus antiquior (Jelly, 1843), and the thecidellinids – two species: Rioultina zalasensis sp. nov. and Rioultina wapiennensis Krawczyński, 2008. The species described herein indicate tropical or subtropical waters, and a moderately (?) deep character of the sea basin at Zalas.
The presented paper contains a detailed description of four species of the genus Craniscus DalI, 1871, found in the Upper Oxfordian of Bielawy and Wapienno quarries, Kujawy area. Three of them: Craniscus bipartitus (Munster, 1837), Craniscus antiquior (Jelly, 1843) and Craniscus corallinus (Quenstedt, 1852) have already been described from Poland, the fourth, however - Craniscus tripartitus (Munster, 1840), had only been known from the Lower Oxfordian of North Bavaria. The Craniscus specimens come from slope deposits of sponge-microbialitic bioherm. This is indicated by the fact that almost all specimens are dorsal valves, separated posthumously from ventral valves. The condition of some specimens and the rock lithology suggests, that the deposition was very violent in some cases and brachiopods were buried alive. The studied material is relatively well-preserved, which alIowes an accurate reading of the location of muscle scal's.
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