Common Name(s): Deep-water sea fan, Black sea fan
Colony Form: Monoplanar stiff fan with dichotomous branches not interconnected; to ~1 m tall.
Axis: Flattened in plane of fan.
Branches: Flattened in plane of fan, dichotomous, not interconnected, 3-5 mm across. Secondary branches and unbranched twigs usually bent. Terminal twigs along fan periphery usually forked. Edges of twig ends folded over and joined so that twig tips are indented or grooved (=fistulose).
Apertures: Polyps restricted to sides of branches. Calices are low oval or slitlike mounds with eight lobes.
Color: Red-brown, copper, dark brown or grey. Often appearing black in situ. Usually light brown when dried.
Sclerites: Polyp armature: flattened, slightly curved spindles to 0.5 mm long, arranged in eight series of inverted V’s (“en chevron”). Outer layer: chiefly elongate spindles 0.5–0.6 mm long, with ornamentation ranging from scattered small thorns to crowded tubercles. Inner layer: smooth to slightly warty, extremely slender needles 0.5–0.7 mm long.
Habitat: Deeper reefs, commonly along slopes, walls, crevices and canyons exposed to currents. Depth range: 3-368 m, usually below ~15 m.
Distribution: Georgia to Brazil, Bahamas, Caribbean Sea.
Notes: Unlike sea fans of genus Gorgonia, I. schrammi branchlets do not interconnect. Fans vibrate in strong currents. The indented or grooved twig tips are unique among shallow, Western Atlantic octocorals.