Hi Rick,
It would help to see a piocture of the fully developed mother colony, as there is not an acropora (exception listed below) that has a fully fused branches without axial corallites growing up out of the plane of the plate, although this specimen could be part of the coenosteum between those corallites.
Acropora branchi is the closest, although
A. glauca, A. solitaryensis, A. retusa, A. orbicularis,and A. clathrata are similar species with interlocking basal branches and rounded radial corallites that form plates to some extent.
Looking through the entire Veron ID key, I could only find one other specie that has fully fused branches, and even it usully has some branching at the edge.
Acropora efforescens colonies are extensive flat plates which are fully solid with the exception of their outer perimeter, whic h usually consists of highly fused irregular branches. Radial and axial corallites are not well-differentiated, and all have sharp rims. All the corallites at the edge are horizontal, however, those on the upper plate surfaces are short, compact, and upward-facing. There is little if any corallite development on the undersurface of the plates. Bad news, they are almost always a uniform dark grey in color, they may or may not have contrasting corallite colors (purple in one example) and are EXTREMELY RARE and are found almost exclusively in the Indonesian archepelego. If it dies, I can positively ID it for you from the skeleton. This will be a good excuse to send me a frag of it.
if the frag dies, I will id it for you
Most likely some spp of Montipora, although I do not think it is
M. capricornis due to the unusual terbucle in the middle of the specimen. Once again, a pic of the full colony is almost necessary to get ID to even the Genus level... (or the skeleton).
HTH
