Acropora insignis
Nemenzo, 1967
Corallum light, caespitose, 27 x 19 cm across, 10-11 cm high; a confused but not very crowded mass of branches and branchlets. Branches arise from narrow, short base, only 1.5 cm across; lax, very proliferous, distantly coalescent, slightly attenuate, cylindrical; one branch 14.5 cm long, 6.5 mm across at base, 4.5 mm about a cm below apex; more than half of length towards base covered with distant subimmersed corallites and occasional projecting or verruciform ones; remaining distal region bears prominent corallites mixed with low ones, just as on terminal branchlets. Lower surface of peripheral, almost horizontal branches has more dispersed, mostly verruciform corallites. Branchlets spiciform, 2-2.5 cm long, 3-4 mm diameter, usually almost at right angle to branch, projecting in all direction so that corallum has tangled appearance.
Axial corallite cylindrical, around 2-2.5 mm diameter, distinctly exsert; wall about half calinical diameter in thickness, porous, costate, rim not rounded. Septa in 2 complete cycles. Primaries short of radius midpoints, directives only slightly distinguishable. Secondaries slightly narrower than primaries.
Radial corallites rather distant on distal portion gradually decreasing in height towards apexl; prominent ones nariform, projecting 1.5 mm, up to 1.5 mm across, rim horizontal so oval calice faces upward; few taller tubular ones bearing buds found here and there. Wall thin, delicate, lacelike, very porous; costate, some older corallites may have few spines. Mixed with tall corallites are low ones, also nariform, becoming flush or subimmersed towards base where they are most abundant. Septa irregularly developed; directives always prominent, confluent at base of fossa of tall radials; other septa (including occasional secondaries) very narrow, represented by rows of spines.
Intercalicinal areas rough; reticulum irregular with ridges bearing distant, foliate or slender spinules; meshes diffused. On younger portion, threads prominent, continuous calicular wall as costae.
Remarks: This is a light, fragile coral. It can be distinguished by relatively slender branches and branchlets which are made very rough on the terminal portions by corallites of very unequal height. Its numerous ramifications projecting in all directions give this coral its very tangled but not crowded appearance. The thin, delicately reticulate calicinal wall is remarkable.