Late Silurian and Early Devonian Beyrichioidea from Gondwana and Perigondwanan terranes and their palaeobiogeographical implications

The Late Silurian to Early Devonian palaeogeography and the question whether there has been a large and deep Rheic Ocean between Laurussia and Gondwana is still a matter of discussion. It has been assumed in many papers that the Rheic Ocean formed a palaeogeographical barrier and, therefore, Gondwana had no common beyrichioidean ostracode faunas with Laurussia before the Emsian. The appearance of ostracodes (particularly the beyrichioideans) in Gondwana at this time should testify the closure of the Rheic Ocean. Although some palaeogeographic reconstructions consider common ostracodes in Laurussia and the Perigondwanan areas Armorica and Perunica in the Lochkovian, they do not refer to occurrences in Gondwana. However, several publications describe late Silurian to Pragian beyrichioideans from Gondwana and adjoined Terranes (Perigondwana), thus questioning the existence of the Rheic Ocean at this time. This paper aims to summarize the occurrences of common beyrichioidean ostracodes from (Peri-)Gondwana and Laurussia in an attempt to provide a reliable data source for future work. The occurrences of beyrichioideans from North Africa, South America, southeastern Turkey, Ibero-Armorica, and the Ossa Morena Zone (Spain) are reviewed and their ages are partially re-dated through correlation with other faunas. The presented results indicate that shallow marine migration paths must have existed, thus strengthening the arguments against the Rheic Ocean.