Palaeozoogeographical connections of the Devonian vertebrate communities of the Baltica Province. Part I. Eifelian–Givetian

Middle Devonian vertebrate communities within the Baltica palaeozoogeographical Province are analysed for intra- and interprovincial connections. Components within the category of provincial endemics are used to assign each community to a particular zoogeographical province. Two types of vertebrate dispersal are outlined: (1) normal marine and (2) coastal, presumably brackish-water (or continental). During the Middle Devonian the marine type is displayed by climatiid and ichnacanthid acanthodians, and the coastal type mainly by psammosteids, antiarchs, porolepiforms, and other acanthodians. Isolation of the communities is reflected by predominance of local and provincial endemics during the Givetian; wider connections are recorded by the majority of cosmopolitans and taxa distributed within a limited number of provinces during the Eifelian. Constant faunal interchanges are observed between Baltica, Laurentia, and Armorica; connections to other provinces are infrequent. Different vertebrate groups show varying dispersal capabilities. The most important cosmopolitans during the Middle Devonian are climatiid and ichnacanthid acanthodians, struniiforms, and arthrodires. Agnathans and sarcopterygians show limited dispersal capabilities.