North Silurian Realm

Figure 34.1 Silurian. I Afro-South American Realm 2-7 North Silurian Realm, North Atlantic Region (2 North American Province 3 European Province), 4 Uralian-Cordilleran Region undivided (5 Sino-Australian Province 6 Mongolo-Okhotsk Province 7 Iran).

Uralian-Cordilleran Region. Occurrences are widespread from the Urals east to include all of Asia, eastern Australia (the limited North Silurian Realm fossils of Western Australia do not permit regional assignment), plus much of Cordilleran and Arctic North America. As stated above, the Carnic Alps-Karawanken area belongs here, presumably being inserted into Southern Europe during the earlier Carboniferous. 

Fossiliferous occurrences are known in northern South America in the Merida Andes of Venezuela, and a few genera of North Silurian type, such as Coelospira, are present in the Argentine Precordillera and Puna, and in a few Bohvian localities. In Africa only northern North Africa is represented, with no fossihferous warm water Silurian known from South Africa. North America, Eurasia and Austraha include numerous, widespread fossil localities belonging to this realm. 

This realm is definitively known exclusively from the southern two-thirds of South America and north-west Africa. The Disa Siltstone fauna of South Africa is now (Boucot, 1999) considered to be of latest Ordovician, Hirnantian age, although an Early Llandovery age was considered earlier. If shallower-water brachiopod faunas of Silurian age are recovered from southern Africa they would be expected to be similar to those of the Afro-South American Realm known from so many South American localities, as is also the case with the Falkland Islands, where Silurian rocks are currently unrecognised. The northernmost occurrence is in the Amazon Basin, with numerous occurrences from the Titicaca region of southern Peru and adjacent Bolivia southerly into northwestern Argentina (in the provinces of Salta and Jujuy). 

---