There are several Acropora species with this general appearance. One of these whose distribution includes the Marshall Islands is Acropora anthocercis, although it is possible that some or all of those figured below are other species. These are found throughout the atoll.
The lowest one in the photo below is what we have figured elsewhere as Acropora cf globiceps.
Those on the reeftop (below) can be exposed to air at very low tides.
Many of these suffered coral bleaching in the 5 or more warm water episodes since 2009. For more on bleaching, see this.
Created 13 December 2020