Family Plexauridae

Remarks: The only specimen examined for this work is a complete, large (35 x 23 cm) colony that was collected by submersible and subsequently dried. In life the specimen was bright yellow but turned black when exposed to air. After drying the colony appeared dirty white but still liberated yellow pigment when exposed to sodium hypochlorite (bleach). The colony shape is fan-like and mostly in one plane, with small, upturned branchlets arising from the main stem, and occasional anastomoses occur. The branch tips are slightly inflated. The main stem at widest is 1 cm and the branches are 2–5 mm in diameter.
The calyces are crowded at the tips of distal branchlets but are sparsely distributed near the base of the colony and on larger branches. The surface coenenchyme contains stout, bent, randomly oriented warty spindles that may reach 0.75 mm. Some spindles have blunt, warty projections. The coenenchyme also contains forked spindles and antler-like plates.  The anthocodial sclerites are in a collaret and points arrangement, with each point consisting of 2–3 bent, thin rods with fine tuberculation. The calyx walls consist of 2–3 series of thornscales, the distal ones forming an armed rim around the opening, giving the colony a “fuzzy” appearance when viewed unaided. The polyps are partially retracted and the armature is exposed.
The thornscales have an echinulate spine and tuberculate base. They vary considerably in size and shape with some approaching almost 1 mm in greatest length. Some thornscales are nearly triangular in shape with a reduced spine and highly-fused base; some scales have a very prominent spine and weakly fused base.  
The thornscale variation has led to difficulty identifying this specimen to a level below genus. The specimen was determined to be a species of Paramuricea based on the amount of fusion of the basal lobes of the thornscales (Bayer 1959a), and the lack of spinous lateral projections on the bent coenenchymal spindles (Bayer, 1959a; Grasshoff, 1977).  The specimen does not unequivocally fit any of the descriptions of Paramuricea species in Deichmann (1936) or Grasshoff (1977) so a species level determination has not been made.

Figure 1. Placogorgia sp, live specimen (SERTC 2922). Scale bar = 2 cm.

Figure 2. Placogorgia sp. live specimen (SERTC 2922), showing stem and calyces.

Figure 4. Placogorgia sp., dried specimen (SERTC 2922). Thornscales from cortex of stem tip (a-d) and base (e, f); forked scales from base (g, h); antler sclerites from stem tip (i) and base (j); curved rods from stem tip (k, l) and base (m,n). Scale bar = 200 µm.