Canda scutata Harmer, 1926

Canda scutata Harmer, 1926 View in CoL

Figure 11 View FIGURE 11

v. 1926 Canda pecten var. scutata Harmer , p.

389, pl. 26, fig. 24.

Figured material. PMC EDM-Collection J.H.B.126a, samples 19200 ( Figure 11A–C View FIGURE 11 ), sample 19029 ( Figure 11D View FIGURE 11 ), and sample 19227 ( Figure 11E–F View FIGURE 11 ); Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Description. Colony erect with narrow (c. 265 µm), rectilinear, biserial, keeled branches; articulating nodes and bifurcations not observed. Autozooids distinct, separated by shallow grooves, rounded rectangular, elongate (mean ZL/ZW 2.13), arranged alternately in two longitudinal, series. Gymnocyst minimal, smooth, convex. Cryptocystal area outlined by a shallow furrow; cryptocyst slightly depressed, occupying slightly less than half of the frontal surface (mean CryL/ZL 0.36), smooth to nodular, granular around the opesia with granules projecting into it, giving a serrated appearance, extensive proximally, narrow laterally nearest branch midline, wider and wedge-shaped on the outer side, absent distally. Opesia asymmetrical, almost triangular (i.e., comma-shaped), tapering proximally, occupying half of the frontal surface (mean OpL/ZL 0.50); a single spine on each distolateral corner, 10–20 µm in diameter at the base, visible also in ovicellate zooids; a spine-base-like structure laterally at about opesia mid-length on the inner side of the branch, with a larger diameter (30–55 µm) than spine bases, appearing to be the base of a detached scutum; spines and putative base of scutum indenting the outline of the cryptocystal area. Vestigial avicularia associated with ovicells, distally placed, rounded triangular, directed distolaterally, alternating on either side. Ovicells globular, relatively depressed, obliquely placed, directed inwards from the opesia, with a pointed distal margin due to the presence of the avicularium; the series of convergent and alternating ovicells from the two zooidal rows forming the central elevated part of the branch. Ooecium smooth; ectooecium with an irregularly elliptical central fenestra, exposing the endooecium. Dorsal side occupied by vibracula with a long, curved, deep setal groove oriented distolaterally; a shallow sinuous median furrow corresponding to zooidal boundaries; a large, circular radicular pore measuring 40–50 µm in diameter, placed proximally on each vibraculum on the outer side.

Measurements (µm). ZL 351±22, 307–395 (4, 20); ZW 165±22, 121–202 (4, 20); OpL 174±12, 160– 194 (2, 7); OpW 60±6, 51–65 (2, 7); CryL (proximal) 128±13, 110–154 (4, 20); VibrL 179±14, 163– 198 (2, 9); VibrW 115±11, 94–134 (2, 9).

Remarks. Harmer (1926) described this species as a variety of Canda pecten Thornely, 1907 , distinguishing it by the presence of minute scuta in the new variety (see also Tilbrook, 2006). The specimens from Daidokutsu cave show the main diagnostic characters of the species, including asymmetrical opesiae and obliquely placed ovicells with associated vestigial avicularia and broad ectooecial fenestra. Branch bifurcations were not observed in the examined samples, which prevented the observation of another key diagnostic feature, i.e., the presence of large frontal avicularia, either single or paired, which are developed on each branch above the bifurcation. Our specimens also lack a scutum, but the attachment base is clearly recognizable ( Figure 11D View FIGURE 11 , arrowed), leading to their identification as C. scutata rather than C. pecten . While C. pecten has been already recorded in Japan ( Tilbrook, 2006), C. scutata had not been previously reported in this region. It has been documented in New Guinea and the Loyalty Islands (Harmer, 1957), the Kermadec Ridge (Gordon, 1984), and the Nansha Islands (Liu, 1991). The specimens illustrated by Gordon (1984, pl. 13D–E) differ slightly from the specimens found in the Daidokutsu cave. The differences include more prominent ovicells with apparently different lengthto-width proportions, varying development of the frontal fenestra, the possible occurrence of a second spine at one distal corner, and narrower vibracula.