Paracalyptrophora enigma, Cairns, Stephen D., 2018

Cairns, Stephen D., 2018, Deep-Water Octocorals (Cnidaria, Anthozoa) from the Galapagos and Cocos Islands. Part 1: Suborder Calcaxonia, ZooKeys 729, pp. 1-46 : 16

Paracalyptrophora enigma sp. n. Figures 3a, 10

Material examined.

Types. Holotype: colony and SEM stubs 2338-2342, JSL-I-1915, USNM 1409703. Paratype: JSL-I-1916, 1 colony, USNM 1409707.

Type locality.

1°17.2'S, 89°48.7'W (northwest of Española, Galápagos), 653 m depth.

Distribution.

Known only from northwest of Española, Galápagos, 547-653 m deep.

Description.

The colony is uniplanar, equally and dichotomously branched, the largest colony (the holotype, Figure 3a) being 17 cm in length and having only 12 terminal branches, none longer than 4 cm. Its broken base is highly calcified and 10.5 mm in diameter. The entire corallum is white. The polyps are arranged in closely spaced (4.5-5 polyps per cm) whorls of seven or eight (Figure 10a), the higher number occurring on larger-diameter basal branches; the whorl diameter ranges from 4.5-6.0 mm. The horizontal length of a polyp is 2.5-2.7 mm.

The basal scales (Figures 10a, e) stand perpendicular to the branch or tilted slightly anteriorly, and extend up to 1.75 mm in length, the distal 0.23-0.28 mm of each basal scale projecting as wide, flat teeth, which are longitudinally ridged on their inner surface (Figure 10d). There is a horizontal articular ridge joining the basal to the medial scales (Figure 10d). Otherwise, the inner surface of the basal scale is highly tuberculate, and its outer surface is smooth and not ridged, as are all the body wall scales. The medial scales (Figure 10f) are as wide as the buccals, 1.10-1.15 mm in length; the distal and lateral 0.25 mm of their inner surface is smooth (but not ridged), the rest highly tuberculate. The buccal scales (Figure 10g) are slightly longer (1.12-1.25 mm) but much wider, curved around much of the operculum in a scalloped shape. The 0.5 mm distal, inner margins of these scales are also smooth and thin, forming a translucent cowl (Figure 10c) surrounding the operculum. The ratio of the major body wall scales is about: 1:0.67:0.77. There is at least one pair of rectangular adaxial scales (Figure 10c), each about 0.37 mm in width. The single abaxial opercular scale (Figure 10h, leftmost) is 0.85-0.90 mm in length and has two broad lateral lobes (producing a very low L:W of 0.75-0.85) and thus being symmetrical, and has a small rectangular base. The much smaller, symmetrical, paired adaxial operculars are 0.75-0.80 mm in length with a L:W of about 2.0. The five lateral operculars range in size from 0.90 to 1.05 mm in length and are asymmetrical, each having a lobe on their adaxial side, the L:W ranging from 1.5-1.6 (Figure 10h). The distal inner half of all opercular scales bears a thin ridged keel, whereas the outer surface is covered with low pointed granules. The coenenchymal scales (Figure 10i, j) are elongate (L:W up to 8) and longitudinally crested (i.e., "sail scales", Figure 10j), the crests up to 0.15 mm in height. The outer surface of these scales is covered with small granules much like that of the operculars.

Comparisons.

Superficially this species resembles the genus Narella , in that it has three pairs of body wall scales, but the distal inner surface of the basal scales have an articular ridge, which is more consistent with the genus Paracalyptrophora , P. enigma being the only species in the genus with three pairs of body wall scales.

Etymology.

Named “enigma” (Latin for inexplicable) because it is the only species in the genus to have three (not two) pairs of body wall scales.