Typically forming large, dome-shaped or plate-like structures up to a metre or more in diameter (1) (3), the colonies of Platygyra lamellina are covered in a maze-like pattern of thick brown ridges, or walls, and grey or green depressions, known as valleys (3). However, as in many related coral species, there may be a wide variety in colony shape and form (3) (4). Coral colonies are composed of tiny, anemone-like animals, known as polyps, which secrete the hard coral skeleton. In Platygyra species, the polyps share common walls, with the polyp ‘mouths’ aligned in the valleys, and the polyps themselves not individually identifiable. The polyp tentacles are usually only extended at night (3).
Platygyra lamellina can be difficult to distinguish from the more common Platygyra daedalea, and the two species have sometimes been classed together in the past. However, Platygyra lamellina has thicker, more sloping walls, which lack a flat top, and has more rounded septa, the radial elements that project inwards from the skeletal walls of the polyps (3) (4) (5).