[Coral-List] mushroom-shaped massive coral colonies

[Bill Allison]

I am looking for publications explaining how mushroom-shaped massive coral
colonies are formed. Explanations supported with empirical evidence are of
particular interest.
I have searched for such papers but have had little luck. I vaguely
remember a paper on the subject based on observations in the Caribbean,
Glynn (1991) attributes such morphology to urchin bioerosion, and Satoh
(2000) suggests sand as an agent.
I wonder if members can help me out.
Regards,
Bill