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New data on the trace fossil, Cruziana semiplicata (Furongian, Wiśniówka Sandstone Formation, Poland) : origin, ethology and producer

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Sadlok G.

tom Vol. 84, No. 1

35--50

Cruziana semiplicata Salter is a well known ichnospecies, ascribed to trilobites. Despite that, there are still contradicting views on its origin (infaunal vs. epifaunal), the ethology represented (crawling vs. feeding) and the identity of its producer (a few trilobite genera were proposed). In this paper, new data are presented and com- bined to create a coherent interpretative model for Cruziana semiplicata. According to this new model, Cruziana semiplicata is a fossilized version of an epifaunal, pascichnial (feeding) trace produced by an organism, positioned above the seabed with only a few frontal appendages touching the depositional surface and processing the sedi- ment below. This model is based on observations of trace fossil morphology and neoichnological observations of the feeding behaviour of Triops australiensis. Also, a short geometrical comparison with the co-occurring Rusophycus polonicus is made to show that these trace fossils most likely had different trace makers.

Trace fossil Cruziana tenella from the Furongian (Upper Cambrian) deposits of Poland

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Sadlok G.

tom Vol. 60, no. 3

349-355

A minute, bilobate ribbon-like trace fossil, assigned to the ichnospecies Cruziana tenella, is recorded for the first time from Furongian (Upper Cambrian) strata of the Wiśniówka Formation exposed in the Wiśniówka Wielka quarry, Holy Cross Mountains, central Poland. The collected material of C. tenella is interpreted as arthropod pascichnia trails. A significant gap in size distribution and morphology between C. tenella and other Cruziana trails from Wiśniówka Wielka suggests that the former cannot be regarded as produced by juveniles of the biotaxa responsible for the latter. C. tenella from Wiśniówka Wielka was most probably produced by arthropods reaching a small adult size.

100%

Sadlok G.

2013

tom Vol. 83, No. 4

317--327

In general, the trace fossil Rusophycus, preserved as a concave-upward structure on the top of a bed, is considered to be a fossilized marking, made by a trace maker. The structures described from the Cambrian (Furongian) of central Poland are genetically related to Rusophycus. However, despite their occurrence on the tops of beds, they are not fossilized traces, but compaction-related features, resulting from differential sandstone and mudstone compaction with possible mediation by organic-rich, heterolithic sediments. The preservation of these structures probably was influenced by biofilms or biomats.