In examining the known occurrence of Cambrian and particularly Ordovician trilobites it has been found that:
Faunas of continents and platforms that have remained in a single latitudinal zone, particularly in a warm climate, show most strongly the effects of local environment. Concentric geographic changes in faunal composition and diversity result, as in North America.
Faunas of continents that passed rapidly through inclement climatic zones bear the print of climatic rather than local environmental variants. Faunas may be arranged in broad latitudinal bands and apparent standing diversities may change stratigraphically within each continental shelf area, as in western Gondwana (Andean area).
Inferred patterns of warm oceanic currents relative to changing continental obstructions are compatible with distribution of pelagic trilobites.
Tethyan trilobite distribution during the Ordovician shows reversals in migration related to (a) movement of Moroccan and Algerian Gondwana into warmer climate, (b) removal of Antarctic and Australian Gondwana from its obstructing position across the equatorial current, (c) westward movement of Baltoscandia, and (d) eastward movement of North America.
Most oil reserves are in areas that have been in warm climates (horse latitudes) at some time in their geologic history. Lands that have spent the longest geologic time in such zones may have the greatest potential for petroleum production, provided that there is adequate stratigraphic cover and satisfactory geologic structure to retain the oil.
Paleobiogeography, here exemplified by trilobite distribution, may make an important contribution to delimiting potential areas for profitable exploration.