An explanation for low endemism of Triassic crinoids from the epicontinental Germanic Basin, Poland

Abstract

A summary of known crinoid taxa in the Polish part of the Triassic Germanic Basin, including their presence elsewhere, is documented. At present, 13 taxa and 3 ecophenotypes of crinoids have been recorded from that area, only one of them being endemic. In the Lower Muschelkalk and lower part of the Middle Muschelkalk, taxa widespread both in the Tethys and Germanic Basin, or Tethyan taxa, dominate. In the Upper Muschelkalk crinoids are very rare in Poland, being represented by Encrinus liliiformis and Holocrinus sp. Many of the species occurring in the central part of the Germanic Basin in the Upper Muschelkalk have not been recorded in the eastern part of the basin. The degree of endemism of the crinoid fauna in the Muschelkalk is markedly lower than the degree of endemism of the rest of the benthonic macrofauna. This probably resulted from huge number of crinoids forming “crinoid gardens” that produced large number of larvae, increasing the chances of successful geographical expansion of crinoids.