Page 55 - Introduction to Paleobiology and The Fossil Record

42 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

Lystrosaurus
Mesosaurus India
Africa

South America
Australia

Antarctica

Cynognathus
Glossopteris
Figure 2.14 Carboniferous and Permian distributions of the Glossopteris fl ora and the Mesosaurus

fauna and the fit of Gondwana. The tight fit of Gondwana and the correspondence of fossil faunas and

floras across the southern continents suggested to Wegener and others that South America, Africa,
India, Antarctica and Australia had drifted apart since the Permo-Triassic. (Based on Smith, P. 1990.
Geoscience Canada 15.)
early 1900s, the German scientist Alfred terozoic Ediacara faunas may have already
Wegener (1880–1930) suggested that the con- developed their own provinces. George
tinents moved across the Earth’s surface on a Gaylord Simpson (1902–1984) distinguished
liquid core, suggesting that continents could three types of passages: corridors were
in fact drift (although not through the oceans open at all times, fi lters allowed restricted
as he thought), some 50 years before the doc- access, whereas sweepstake routes opened
umentation of seafloor spreading and the only occasionally. In continental settings the

plate tectonic revolution confi rmed his theory barriers may be mountain ranges, inland
(Wegener 1915); such data continue to be seas or even rain forests. Marine faunas
accumulated today as an integral part of may be separated by wide expanses of deep
paleogeographic analysis (Fortey & Cocks ocean, swift ocean currents or land. In general
2003). Our understanding of plate move- terms the endemicity of most marine faunas
ments has been greatly advanced by a number decreases with depth; the more cosmopolitan
of computerized paleogeographic systems; faunas are located in deep-shelf and slope
some, such as the Paleomap Project, even environments. But in the deeper basins, popu-
taking the Earth far into the future as well as lated by specialized taxa, faunas are again
deep into the past (linked at http://www. endemic.
blackwellpublishing.com/paleobiology). Faunal or floral provinces may be frag-

mented relatively rapidly if a barrier
arises and the biotic responses may be quite
Faunal and fl oral barriers
sudden. For example, rifting and basin
Barriers of various types have partitioned bio- formation can split and isolate into fragments
geographic provinces through time. The fi rst many existing terrestrial and fringing shelf
large-bodied organisms of the Late Neopro- provinces, whereas the same effects in the sea