FAMENNIAN VERTEBRATE BIOGEOGRAPHY EMPHASIZING EURAMERICA: SOUTH MARGIN (PENNSYLVANIA, BELGIUM) VS INLAND (EAST GREENLAND)

Late Devonian biogeographic patterns of marine faunas are relatively well understood compared to those of continental faunas. Despite the incompleteness of the rock record, the fossil richness of some terrigenous localities allows biogeographic considerations. As an example, vertebrate faunal assemblage comparisons of the outstanding Famennian tetrapod-bearing localities of East Greenland, Pennsylvania and Belgium provide important results. These Upper Devonian continental sediments have yielded representatives of most major groups of fossil vertebrates, including placoderms, acanthodians, chondrichthyans, actinopterygians, and sarcopterygians (lungfishes, porolepiforms, osteolepiforms, rhizodontids, and tetrapods). The three localities show considerable faunal overlap at genus level although some remarkable differences also occur. For instance, the placoderm Remigolepis is present in East Greenland but seems to be absent in Pennsylvania and Belgium. On another hand, the rhizodontid and megalichthyid sarcopterygians (both of Gondwanan origin) are present in Pennsylvania and Belgium but not in East Greenland. An Ichthyostega-like tetrapod is present in Belgium, a genus previously only known in East Greenland associated with Acanthostega. The locality of Red Hill, Pennsylvania, has yielded at least two tetrapods (Hynerpeton and Densignathus) significantly different from Ichthyostega. The possible paleogeographic and/or paleoenvironmental causes (inland fluviatile floodplain facies of East Greenland versus estuarine floodplain facies of Pennsylvania and Belgium) of the differences cited above (and others) are discussed. This study suggests close relations, most probably by hydrographic links, between the inland part (East Greenland) and the south margin (Belgium and, on a lesser extent, Pennsylvania) of Euramerica. Presence of fishes of Gondwanan origin also suggests close geographic relations between Euramerica and Gondwana during the Late Devonian times.