Occurrence
Rich collections have been found in China, Mongolia, Kazakhstan, Australia, and Antarctica; and moderately diverse ones in India, Pakistan, Iran, Europe and North America. There are different views about the time range of the SSFs. The Russian discoveries of the late 1960s were assigned to the Tommotian age of the Cambrian period, and for some time the term "small shelly fauna" was applied only to that age. On the other hand Bengston includes in "SSF" Ediacaran fossils like Cloudina and post-Tommotian fossils like Microdictyon from the Maotianshan shales lagerstätte. SSFs have been found in layers that also contain fossil trilobites. The mass extinction at the end of the Cambrian period's Botomian age was thought to have wiped out most of the SSF, with the exception of the halkieriids, wiwaxiids and Pojetaia.
Read more about this topic: Small Shelly Fauna
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