Since Muschelkalk crinoids were stenohaline and required hard substrates to get attached, they could settle continuously only on paleohighs near the connection to the Tethys. In Upper Muschelkalk times they managed to spread from these centers throughout the western parts of the basin as bottoms became shelly due to regressive conditions. In the Lower Muschelkalk basin continuous settlement was possible only near the eastern gates, from where crinoids spread to the West together with the oolitic Schaumkalk facies. In contrast to the less substrate-controlled ceratites and conodontophorids, crinoids fail to show endemic evolution.