Common Name(s): Giant slit-pore sea rod, Nodding plexaurella
Colony Form: Colonies usually tall with few long branches in multiple planes; to 1.5 m tall.
Axis: Extensively mineralized by calcite, up to 85% mineral aggregate at branch tips; aggregates up to 5 mm in length and embedded longitudinally in the gorgonin (Lewis et al. 1992).
Branches: Sparse, dichotomous; terminal branches 10-15 mm across and up to 1 m long; tips usually somewhat enlarged or bulbous.
Apertures: Distinctly slit-shaped apertures; calices form widely separated hemispherical mounds.
Color: Tan, light brown to mauve; putty-gray or light brown in alcohol.
Sclerites: Polyp armature: strong; blunt rods to 0.3 mm long. Axial layer: spindles, crosses and capstans, the latter often with two longer rays, 0.15-0.25 mm long. Middle layer: large, slender spindles, triradiates, 4-radiates, to 0.45 mm across. Surface layer: capstans usually with two longer rays, 0.075-0.2 mm across.
Habitat: Inshore patch reefs to outer slope and fore reefs, from 4 to >30 m depth.
Distribution: South Florida, Bermuda and throughout the Caribbean Sea.
Notes: Grows taller than either P. dichotoma or P. grisea, and with more widely spaced apertures that are always elevated. Distinguished by large quadriradiate sclerites (to 0.5 mm across) with slender arms in the middle layer. Polyps are armed more heavily than any other Plexaurella with stout rods (0.3 mm long) (Bayer 1961). Preyed upon by the generalist octocoral predatory snail Cyphoma gibbosum, but also by Cyphoma signatum, a specialist predator on Plexaurella spp. (Ruesink and Harvell 1990).