Masowe nagromadzenie artykulowanych szkieletów wężowideł w osadach środkowego triasu Górnego Śląska i ich implikacje tafonomiczne

Abstract

Mass-occurrence of articulated skeletons of Middle Triassic ophiuroids from the Upper Silesia and their taphonomical implications (southern Poland).S u m m a r y. Due to their poor fossilization potential, fully articulated ophiuroids are extremely rare in the fossil record. Therefore much of their evolutionary history is based on the study of isolated skeletal elements. In this paper the mass-occurrence and taphonomy of articulated ophiuroids from the Middle Triassic of Wojkowice, Upper Silesia (S. Poland) is described. The assemblages consist of monospecific and multiindividual beds with small ophiuroids Aspiduriella similis (Eck). Among 134 analysed specimens, 86 % are partially disarticulated, without distal and middle parts of their arms. Nearly all specimens are preserved with their oral side turned up. The high percentage of articulated specimens embedded within thin, fine-grained layer underlied by biomicrites with a few crinoid ossicles, indicates rapid burial in the deeper part of the shelf, below the crinoids habitat, caused by high-energy (storm) event in a shallow part of the basin. Apart from palaeobiological merit, such obrution deposits, characteristic for many Konzentrat–Lagerstätten accumulations, are very useful in recognizing the sedimentary environment dynamics and in stratigraphic correlations.