PALEOBIOGEOGRAPHY OF THE MARINE REALM 169 



Interpretive Basis of Marine Paleobiogeography 



General Probabilities 



Those familiar with the geographic distribution, sedimentary 

 associations, and nature of the fossil marine biotas recognize that 

 parallels can be drawn with the distribution of modern marine 

 organisms. Some paleobiogeographic generalizations that appear 

 to apply over a wide range or all of fossiliferous time are listed on 

 Table I. With the exception of No. 14, these categories are not 

 considered further. The citation of case histories would only 

 document associations that follow from distribution characteristics 

 already discussed, and I have reviewed the more specifically 

 ecologic principles and methods elsewhere (Cloud, 1959b). It is of 

 more interest in the present context to get on to subjects involving 

 latitudinal zonation and orientation, for which a brief review of 

 paleoclimatology is prerequisite. 



Paleodimotologic Essentials 



Paleobiogeography, in fact, may be characterized as the mirror 

 of paleoclimatology, in which the blemishes that make it interesting 

 are due to geographic or physiographic (including geomorphologic, 

 bathymetric, and substratal or faciological) isolation, the filtering 

 properties of migration routes, and the intrinsic properties of 

 biologic systems — giving rise to the provincial categories recog- 

 nized by the Termiers (1957, 1959, pp. 81-98) and listed at the 

 right side of Table I. 



Climate itself depends on the circulation of the atmosphere 

 (Fig. 6) and the sea (Fig. 5), the distribution of land and water, 

 the position and inclination of the earth's rotational axis, the 

 composition of the atmosphere, the path of the earth about the 

 sun, and on strictly solar manifestations. Wexler (1957) has 

 summarized modern concepts of atmospheric circulation; Tre- 

 wartha (1954) has discussed the elements of modern climate; 

 Landsberg (1958) has reviewed recent climatic trends; and Brooks 

 (1949), Schwarzbach (1950), and Lasareff (1929) have suggested 

 physical methods for deducing ancient climates. Shapley et al. 

 (1953) have reviewed possible causes, effects, and evidences of 



