It seems that if coral colonies were going to adapt sufficiently to survive above the tidal zone, we would no longer be describing corals but a newly evolved species ...

For a long time, geologists and palaeontologists have used fossil corals and reefs as an indicator of the environmental setting ... it was believed that all corals existed within a fairly narrow range of temperature and depth limits ... so that a fossil coral community indicated a warm shallow marine environment ...

Recent living coral discoveries must challenge that view somewhat ... cold deepwater corals have been found off Norway and in other parts of the Atlantic ... and some of these appear to be closely related (think identical) to some of the fossil forms ... one conclusion proposed is that these ancient corals did not die out but migrated to the deepwater environments and the more recent forms filled the niches thus created ...

but I wonder if these ancient corals were always deepwater forms, and the modern corals expanded into the shallow regions? ... of course, to consider that means overturning some longstanding beliefs about a number of geological settings ... and finding valid explanations for the underlying and overlying strata ... plus a plausible mechanism for vertical transport without destroying the fossil structures ...

so, a third possibility is that the ancient corals were pandemic, and occupied all marine settings ... and lost the warm shallow regions to modern forms, leaving only the deepwater settings where modern corals cannot survive ...

sorry ... just rambling on about the versatility of corals over time ...

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