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Archaeocyatha
Archaeocyatha or archaeocyathids ("ancient cups") is a taxon of extinct, sessile, reef-building〔Archaeocyathid reef structures ("bioherms"), although not as massive as later coral reefs, might have been as deep as ten meters (Emiliani 1992:451).〕 marine organisms of warm tropical and subtropical waters that lived during the early (lower) Cambrian period. It is believed that the centre of the Archaeocyatha origin is in East Siberia, where they are first known from the beginning of the Tommotian Age of the Cambrian, 525 million years ago (mya). In other regions of the world, they appeared much later, during the Atdabanian, and quickly diversified into over a hundred families. They became the planet's very first reef-building animals and are an index fossil〔http://facstaff.gpc.edu/~janderso/historic/paleolif.htm〕 for the Lower Cambrian worldwide.
== Preservation ==
The remains of Archaeocyatha are mostly preserved as carbonate structures in a limestone matrix. This means that the fossils cannot be chemically or mechanically isolated, save for some specimens that have already eroded out of their matrices, and their morphology has to be determined from thin cuts of the stone in which they were preserved.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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