Tennessee River and Crawfish Distribution 



143 



Fig. 1 1. Distribution of Procambarus {Scapulicambarus). Arrow as in Figure 1 

 Horizontal rulings = P. (S.) clarkii. 



Mineralogic data argue strongly that the southern Appalachian high- 

 lands had a significant role in contributing to sediments of the central 

 Gulf Coastal Plain, probably via a major river — the "upper" 

 Tennessee — until late Pliocene times (Isphording 1983). 



It is difficult to imagine that a vigorous Cambarus and Orconectes 

 stock established in the southern Appalachians or on the Cumberland 

 Plateau would not exploit this route (or routes) for the invasion of the 

 newly emerging habitats. Thus, either the two genera were well estab- 

 lished and diversified by the end of the Miocene or they did not emerge 

 until Pliocene times. Logic favors the former thesis. Otherwise, craw- 

 fishes would be undergoing speciation at a rate not supported by any 

 other evidence. 



A Miocene intrusion in Mississippi to within 50 km of the Tennes- 

 see boundary (May 1981, Murphey and Grissinger 1981) is a signifi- 

 cantly different situation than previously assumed. As Murphey and 

 Grissinger (1981) indicated, the Eocene (and probably subsequent) 

 drainage patterns have been buried. Surely, the influential Miocene 

 uplift had profound effects on the freshwater drainage. A very fruitful 

 area for study exists in Alabama and Mississippi. Detailed analysis of 



