Vertebrate Palaeodistributional Patterns and Continental Drift

The patterns of distribution of vertebrates (primarily terrestrial forms) are analysed from the Silurian onwards, using palaeogeographical maps which show epicontinental seas as well as intercontinental oceans. Silurian vertebrates (fish) are known almost exclusively from Euramerica. Many Devonian fish which are normally found in fresh waters seem to have been able to cross intervening seas between one continent and another. It is suggested that this ability may be physiologically related to their capacity to use aerial respiration. There is some evidence for a separate Devonian osteostracan fish fauna in China. Amphibians are first known from the uppermost Devonian of the Euramerican continent, and land vertebrates are known almost exclusively from that continent until the Mid Permian. It is suggested that tetrapods may have evolved in Euramerica, and were only able to colonize Asia and Gondwanaland after continental drift had linked these areas with Euramerica, causing the Uralian and Alleghanian orogenies.