Abstract Devonian rocks are exposed in every region of Thailand, commonly occurring in thick sequences of Lower to Upper Palaeozoic sedimentary and volcanic rocks (Fig. 4.1 ). However, a scarcity of marker fossils and generally discontinuous exposures have meant that Devonian rocks are frequently not distinguishable from older and younger rocks. In such cases, the Department of Mineral Resources (the DMR) have inferred Devonian rocks to be present and have mapped them as Silurian-Devonian, Silurian-Carboniferous, or Devonian-Carboniferous ( DMR 1999 ).

Abstract The succession of Pridolian to lower Eifelian (uppermost Silurian to lowermost Middle Devonian) rhynchonelliformean brachiopod faunas from the Rhenish Massif (Germany) is described and interpreted against the background of sedimentary sequences and facies development. The predominant rhenotypic (‘Rhenish’) facies is redefined as a neritic-siliciclastic facies type of the Devonian. It is subdivided into eurhenotypic, pararhenotypic and allorhenotypic subfacies, based on sedimentary features and specific brachiopod assemblages reflecting different shallow-marine palaeoenvironments under more or less terrigenous influence. The studied sedimentary successions are subdivided biostratigraphically on the basis of brachiopods, correlated on a supraregional scale, and calibrated in terms of the global chronostratigraphy. Stratigraphic intervals with characteristic brachiopod faunas are distinguished. Faunal turnovers between these are attributed to regional events in the context of short or more extended phases of palaeoenvironmental change presumably caused mainly by sea-level fluctuations in combination with varying crustal subsidence and sedimentation rates. These changes resulted in shelf-wide or more regional extinction or emigration of substantial parts of a brachiopod fauna and subsequent replacement by a largely new one. Finally, new taxa of brachiopods are introduced: Sartenaerirhynchus gen. nov., Paraspirifer ( Mosellospirifer ) subgen. nov., Paraspirifer ( Laurentispirifer ) subgen. nov., Iridistrophia ( Flabellistrophia ) subgen. nov. and Iridistrophia ( Flabellistrophia ) musculosa sp. nov.