"Spirorbis" z jeziornych osadów węglonośnego karbonu niecki śródsudeckiej

Krzysztof Mastalerz

Abstrakt


"SPIRORBIS" FROM LACUSTRINE DEPOSITS OF THE COAL-BEARING CARBONIFEROUS OF THE INTRASUDETIC DEPRESSION (SW POLAND)

Summary
A new fiding of fossil fauna from the coal-bearing Żacler Formation (Westphalian) of the Intrasudetic Basin (SW Poland) is being reported. The fiding comprises over 80 moulds, mostly external, and impressions of spiral tubes, which display subtle ridges on their surfaces (Figs 1, 2). Diameters of the spirals range from 0.4 to 2.2 mm. The fossils show bimodal size distribution and diversity of the spiral forms. The fossils resemble calcareous tubes that were commonly assigned to the genus of Spirorbis Daudin 1800 (Polychaeta, Annelida). However, the original materials of the tubes have been dissolved, whichmakes fossil identification not satisfactory. One can not exclude their affinity with gastropods ortentaculites (e.g. Burchette & Riding, 1977; Weedon, 1990, 1991, 1994). The individuals are associated with plant impressions and appear to be attached to the plant fragments before burial. The living organisms were suspension feeders and belong to sessile benthos. The very associated deposits show evidence of a slow, and partly rhythmic, suspension fallout from a water column with no signs of traction. The occurrence of "Spirorbis" and sedimetologicalevidence both point to the unique conclusion, that some deposits of the Żacler Formation accumulated in shallow lacustrine environment.

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