Acta Palaeontologica Polonica 44, 1, 93-115 (1999)
Middle Triassic ammonoids from Silesia Poland.

Kaim, A. & Niedzwiedzki, R.

Abstract. A description of new ammonoid specimens (Acrochordiceras aff. damesi, cf. Acrochordiceras sp. indet., Discoptychites cf. dux, Paraceratites cf. trinodosus, cf. Balatonites sp. indet., Beneckeia buchi) from Lower Muschelkalk (Anisian, Middle Triassic) of Silesia (southern Poland) is presented. The description is supplemented with a list of all hitherto found species of ammonoids in Silesia, which was a southern part of the Germanic Basin during Anisian. Beneckeia and Noetlingites are typical of epicontinental seas and appear usually at the early part of transgression. Other ammonoids entered from the Tethys into epicontinental sea of the Germanic Basin during maxima of transgressions. Some of them (balatonitids, paraceratitits, bulogitids, Discoptychites cf. dux, and probably Acrochordiceras aff. damesi) were successful colonizers which established their own populations in Germanic Basin and evolved towards morphologies typical for epicontinental seas. Other (Beyrichites sp., Paraceratites binodosus and ?Trachyceras sp.) are regarded as unsuccessful immigrants or empty shells drifted post-mortem from the Tethys.