PALEOBIOGEOGRAPHY OF THE MARINE REALM 



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Fig. 9. Xomenclatural identities among described shelly marine benthos in 

 Early Devonian of Southern Hemisphere compared with different patterns of 

 distribution among the living shelly benthos and an Oligocene Tethyan pattern. 

 A (Dall, 1889; Durham, 1952) andE (Keen, 1937; Durham, 1952), transoceanic, 

 subtropical to temperate; B and C (Caster, 1952, pp. 114-116), Devonian, in 

 question; D (Cloud, 1959a, p. 395), transoceanic, tropical with island stepping 

 stones; F (Durham, 1952), across north-south isthmian barrier, tropical; G (Dur- 

 ham, 1952), north-south shoreline, temperate; H (Durham, 1952), middle Cenozoic 

 (Oligocene) east-west Tethyan shoreline. 



(1952) urged, that other factors be considered in interpreting 

 the impressive degree of nomenclatural identity between southern 

 hemisphere Devonian marine faunas. Not only are the described 

 faunas small but also, being from similar Paleozoic rocks and 

 relatively inactive areas paleontologically, they are likely to be 

 conservatively identified and biased in the direction of the more 

 conspicuous, more readily identifiable species, and the brachiopods. 

 Perhaps more nearly comparable data would be obtained if, for 

 instance, among the modern Indopacific faunas one were to 

 identify only the cypraeids and cones. The identities from Saipan 

 to Cocos-Keeling (Fig. 9D) would then rise to from 40% to 70%, 

 across more than 3000 miles of ocean and three opposing east-west 

 current systems — a degree of similarity fully as remarkable as that 

 of the southern hemisphere Devonian, even allowing for the shoal- 

 water stepping stones between. 



Assuming no crustal drift or foundering, we might expect to find 



