Palaeozoogeographical connections of the Devonian vertebrate communities of the Baltica Province. Part II. Late Devonian

Late Devonian vertebrate communities within the Baltica zoogeographical Province are analysed for intra- and interprovincial connections. Components within the category of provincial endemics are used to assign the communities to a particular zoogeographical province. Marine and continental, presumably freshwater types of vertebrate dispersal are outlined. During the Late Devonian marine dispersal is displayed by ptyctodonts, struniiforms, and some dipnoans, and continental dispersal by psammosteids, acanthodians, and some arthrodires. Isolation of communities is reflected by predominance of local and provincial endemics; the majority of polydemics and cosmopolitans records wider connections. It is suggested that proportions of endemism-cosmopolitanism significantly correlate with sea-level changes. Augmentation of endemism may result from regressions that increased isolation of faunas. Separation from the main sea basin may have reduced competition, resulting in radiation within limited areas. Constant faunal interchanges are observed between Baltica and Laurentia, but connections to other provinces are sporadic. Different vertebrate groups indicate varying dispersal capabilities. The cosmopolitans are ptyctodont, arthrodire and antiarch placoderms, chondrichthyans, acanthodians, actinopterygians, and struniiforms. Agnathans and other sarcopterygians show limited dispersal capabilities. Continental and pelagic marine faunas may have interacted by penetration of the members of one fauna into the habitat of another one during favourable periods.