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Vertebrate Palaeodistributional Patterns and Continental Drift

C. Barry Cox
Journal of Biogeography
Vol. 1, No. 2 (Jun., 1974), pp. 75-94
Published by: Wiley
DOI: 10.2307/3037956
Stable URL: http://www.jstor.org/stable/3037956
Page Count: 20
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Vertebrate Palaeodistributional Patterns and Continental Drift
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Abstract

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 envolved 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. The tetrapod fauna of the Upper Permian and Triassic appears to have been cosmopolitan. Though Pangaea started to break up in the Jurassic, land vertebrates were still able to disperse between Euramerica and Asia (probably via the Bering region) and between the Northern and Southern Hemispheres (probably via southern Europe). There is little evidence that dinosaurs were able to cross the Cretaceous Tethyan sea barrier between Laurasia and Gondwanaland. Lower Cretaceous dinosaurs were able to disperse throughout the Northern Hemisphere, presumably by a continuation of the Bering link. In the Upper Cretaceous, the Mid-Continental Seaway of North America, together with the Turgai Straits between Europe and Asia, separated two land areas with distinct dinosaur faunas: `Asiamerica' (Asia plus western North America) and `Euramerica' (eastern North America plus Europe). A barrier appears to have formed between Asia and western North American in the Uppermost Cretaceous. Both marsupials and condylarth placental mammals appear to have crossed between Laurasia and Gondwanaland in the Upper Cretaceous; their route is uncertain, but a trans-Caribbean island sweepstakes route seems the most likely. Marsupials probably entered Australia from South America via Antarctica, placentals evolving later and being unable to follow them because the South America-Antarctica link had by then broken. The apparent areas of origin of the different mammalian orders are shown in Venn diagrams. The history of the faunal relationships of the mammal faunas of the different land masses during the Tertiary is outlined.

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