Thorn Coral

zooxanthellate

Colonies are small, rarely over 30 cm across, with calices about 1 mm in diameter. The two cycles of 6 septa each are markedly different in size. The pillar associated with each calice are also well developed and conspicuous. These readily distinguish this coral from other encrusting species in the region, and being styliform, are appreciably different also to the calical hoods of the encrusting Stylophora species with which it is most likely to be confused. Mostly between 5 and 50 m deep on reef slopes. It is found equally on clear water, exposed reefs and on back reef slopes, in lagoonal and turbid habitats. Its living colour may be green or yellowish brown. (Sheppard, 1998 ) Calices are about 0.8 mm in diameter and are flush with the coenosteum. Septa are in two very unequal cycles. Colour: Dark or pale greenish-brown, with white polyps. Abundance: usually uncommon but more abundant than S. armata. Large colonies (greater than 0.5 m in diameter) are found in higher latitudes only. (Veron, 1986. ) Forms encrusting, columnar or massive colonies with club-shaped knobs and sunken corallites (0.6-1 mm across). Colour: usually pale brown or darker. Habitat: cooler, often turbid shallow reefs. (Richmond, 1997)