Ramienionogi warstw terebratulowych (środkowy trias) zachodniej części Górnego Śląska

Abstract

 Z warstw terebratulowych (środkowy trias - dolny wapień muszlowy) zachodniej części Górnego Śląska opisano 8 gatunków ramienionogów należących do 7 rodzajów terebratulidów, rhynchonellidów i spiriferidów. Stwierdzono występowanie 3 gatunków nieznanych dotychczas z warstw terebratulowych tego obszaru, co wskazywałoby na szerszy zasięg ich geograficznego występowania; dla 2 gatunków określono szerszy zasięg czasowy.

THE BRACHIOPODS FROM THE TEREBRATULA BEDS (MIDDLE TRIASSIC) IN THE WESTERN PART OF UPPER SILESIA

The results of the palaeontologic investigations of brachiopods from the Terebratula Beds (Lower Muschelkalk, Middle Triassic) in the western part of the Upper Silesia have been given (Fig. 1). The collection has contained about 2000 shells of the brachiopods belonging to 7 genera of terebratulids, rhynchonelloids and spiriferoids (Table I, II). The following genera have been found: Coenothyris vulgaris (Schlotheim), Tetractinella trigonella (Schlotheim), Decurtella decurtata (Girard), Hirsutella hirsuta (Alberti), Punctospirella fragilis (Schlotheim), Aulacothyris angusta (Schlotheim), Angustothyris angustaeformis (Boeckh) and Aulacothyroides sp. The acknowledged presence of the last three genera has broadened the extension of their distribution in time (Table 1) and their geographic occurrence. The state of preservation of the shells has been good. Most of the specimens have been complete, consisting of two valves. The ribs of the ornamented forms have been well preserved. The state of preservation of the skeleton parts in the internal structure has been variable. The hinge elements in the hidden part of the shell has usually been preserved (Figs. 2-7). but of the brachidium has been more often preserved in younger forms. In the grown specimens the brachial loop and its fore part have been damaged and broken (especially in C. vulgaris).

The shells of the brachiopods investigated have belonged to the different stages of development and have represented either the juvenile ( C. vulgaris, T. trigonella, D. decurtata), or grown, and even senile stages (C. vulgaris, T. trigonella). Some species have been poorly presented (A. angusta, A. angustaeformis, Aulacothyroides sp.); others, as for instance C. vulgaris, have occurred plentifully. C. vulgaris has probably found the optimal conditions of development in shallow and mobile waters, in which it has settled down during the sedimentation of the Terebratula Beds.