Serpent Coral

zooxanthellate

Colonies in the Red Sea are foliaceous and encrusting. They may form perfect discs or vases with very long and even, concentric valleys (the classical "speciosa" form), or they may develop irregularly contorted sheets with short, broken series, one fairly extreme example of which is illustrated. This degree of contortion, however, stops short of fully ramose development seen in some P. rugosa, but without a lens to examine the columella these may be mistaken for the latter. This is a common species, found mostly in deeper water, mainly on steep to sheer reef walls between 20 to 45 m deep, or in other darker reef habitats. It is mostly limited to clearer water areas, and it commonly coexists with Leptoseris. (Sheppard, 1998 ) Colonies are unifacial laminae, usually horizontal, but may develop upright ridges or columns. More than one row of corallites may occur between ridges. Columellae are absent. Colour: pale brown to deep grey. Abundance: common over a wide range of habitats, colonies are seldom over 2 m in diameter. (Veron, 1986 ) Colonies plate-like (or partly encrusting) with marked linear arrangement of the inter-corallite septo-costae. The pronounced ridges, which are concentric to the margin of the colony, are distinctive. Colour: beige, grey or light brown. Habitat: diverse, including reef bases. (Richmond, 1997)

Corallum: Unifacial and encrusting with foliose margins (Figure 1e) to laminar, sometimes forming tiers of laminae (Figure 1d). The corallum surface is corrugated due to the presence of mostly concentric continuous carinae (Figures 1d–g, 3a–d). Calices: Arranged in rows, mostly indistinct although sometimes polyp mouths can have a distinct coloration in vivo (Figure 1g) allowing recognition of the position of the single calice underneath. Rows generally long and continuous (Figures 1d–g, 3a–d). Series of calices are arranged parallel to each other, concentric and separated by carinae with variable vertical development and inclination with respect to the corallum surface (Figures 1d–g, 3a–d). When asymmetrical, carinae are inclined towards the margin of the corallum. Columella: Well-developed, low-lying in the valleys between carinae formed by the fusion of spatula-shaped processes extending from the inner end of the radial elements (Figure 3e). Radial elements of the higher order form larger processes alternating with the smaller ones from the elements of lower order (Figure 3e). In the same series of calices the processes forming the columella can be separate (Figure 3e) or completely fused (Figure 3f). Radial elements: Radial elements are continuous across the carinae, regularly spaced and equal or slightly alternating (Figure 3c–d). Lateral faces bear regularly distributed, parallel lines of granules or/and menianae. Such lateral ornamentation is variable and includes groups of clumped granules (Figure 2h), menianae with minutely beaded edges and vertically fused granules forming structures similar to menianae but oriented perpendicularly rather than parallel to the radial element margin (Figure 3g–h). The upper margin of the radial elements is minutely beaded and typically attains a zigzag pattern with lateral ornamentations at the angles (Figure 3g–h). This pattern can be so pronounced in some specimens as to give the radial elements a “wavy or even crenellated” appearance to the naked eye (Veron and Pichon 1980: 84; Scheer and Pillai 1983).

Holotype: USNM 119 (Figures 2a, c). Type Locality: East Indies (U.S. Exploring Expedition).