The Domerian sections from the Lusitanian Basin of São Pedro de Muel, Rabaçal and Tomar have provided us with more than
1100 Ostracods belonging from 18 genus and about 48 species. The faunal diversity and density of the associations decrease in
space (from Tomar to Rabaçal and São Pedro de Muel) and time, with favourable environments for the proliferation of Ostracods at the lower part of the sections (Stokesi subzone) and more hostile at the upper part (Ragazzonii subzone). The Monestieri and Nitescens horizons and the Subnodosus subzone are characterized by a typical assemblage of Ostracods.
The palaeoecological Ostracod indexes reveal the fluctuations of the oxygenation, temperature, depth and hydrodynamism of
the water, on the different sections and on the whole platform. They display a diachronous cooling in the Lower Domerian series. In the upper part of the Middle and in the Upper Domerian, the deeper, less oxygenated and cooler waters prevent the development of the Ostracod faunas
