Celleporaria cf. calva Tilbrook, 2006

Celleporaria cf. calva Tilbrook, 2006 View in CoL

Figures 53 View FIGURE 53 , 54 View FIGURE 54

cf. 2006 Celleporaria calva Tilbrook , p. 140, pl.

25D–F.

cf. 2017 Celleporaria calva Tilbrook ; Dick and

Grischenko, p. 181, fig. 12.

Figured material. PMC EDM-Collection J.H.B.144a. Colonies without spines: samples 19125 ( Figure 53A View FIGURE 53 ) and 19114 ( Figure 53B–D View FIGURE 53 ). Colony with spines: sample 19127 ( Figure 54 View FIGURE 54 ). Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Description. Colony encrusting, multiserial, multilaminar. Autozooids distinct or indistinct; when distinct, separated by shallow furrows between very thin, raised rims, irregularly polygonal, slightly longer than wide (ZL/ZW 1.13 with spines, 1.17 without spines), chaotically arranged. Frontal shield convex, coarsely, densely and evenly tuberculate with rounded tubercles measuring 20–30 µm in diameter, imperforate except for a peripheral row of circular, marginal areolar pores, each 22–28 µm in diameter. Orifice hoof-shaped with curved distal and straight proximal margin, nearly equidimensional (mean OL/OW 0.97 with spines, 0.83 without spines), with rounded condyles placed proximally, at reduced distance from the proximal orifice margin (c. 20–25 µm); a shelf-like peristome developing proximolaterally; oral spines present or absent, when present 2–4 spine bases (more commonly three) distally and distolaterally, 20–50 µm in diameter, the proximalmost pair with more robust bases. Avicularia vicarious, with rostrum parallel sided or slightly spatulate, randomly directed, obliquely placed on large cystids with the same frontal texture and sparse marginal areolae as the autozooids; avicularian opening rounded triangular, with a complete crossbar. In the smallest fragment found, consisting of two avicularia and one autozooid, the avicularia flank the autozooid and are distolaterally directed, one rostrum touching and indenting the lateral margin of the autozooid orifice. Ovicells not observed.

Measurements (µm). Colonies without spines: ZL 538 (1, 1); ZW 476 (1, 1); OL 174±4, 171–177 (2, 2); OW 179±1, 179–180 (2, 2); AvL 508±42, 478– 571 (2, 4); AvW 198±25, 174–232 (2, 4). Colony with spines: ZL 497±49, 462–532 (1, 2); ZW 426±7, 421–431 (1, 2); OL 152±16, 132–175 (1, 5); OW 185±18, 167–207 (1, 5); AvL 300±93, 212–456 (1, 5); AvW 99±46, 74–181 (1, 5).

Remarks. Celleporaria calva was first described from the Solomon Islands ( Tilbrook, 2006) and has since been reported from Okinawa at two sites: Sesoko Island and Minna Island (Dick and Grischenko, 2017). Colonies found at Sesoko Island lacked spines, like the nominal species, while those from Minna Island had two oral spines. Despite this difference, all other features matched, leading the authors to classify the two morphotypes as the same taxon. We encountered a similar situation and decided to interpret colony fragments lacking oral spines as well as the single colony having oral spines as belonging to the same species. The absence of spines appears to be genuine. In some zooids spines were obscured by spreading calcification from the distal zooid (e.g., Figure 54B View FIGURE 54 with spines), but traces of their presence were always evident. In the two specimens lacking spines, they could be concealed behind the peristome, yet there is no sign of them in any of the zooids, not even in the larger fragment ( Figure 53A View FIGURE 53 without spines). Our specimen with spines differs from the Minna Island specimen in having 2–4 spines instead of consistently having two. All colonies from Daidokutsu (i.e., with and without spines) share the granular texture of the frontal shield and the hoof-shaped orifice, although the condyles are not obvious in the colony without spines. They also share the development of a shelf-like proximal peristome. The shape of the interzooidal/vicarious avicularia differs between the colonies. The colony with spines has a rostrum with parallel sides, while the one without spines has a more spatulate shape. However, Celleporaria calva from Okinawa, as described by Dick and Grischenko (2017), possesses both types of avicularia within the same colony. This suggests that the presence of only one type in our fragments may simply be due to the small and poorly preserved nature of our specimens. Given the fragmentary state and lack of ovicells in our specimens, we have decided against splitting the species or introducing a new species for the colonies with spines. Instead, we adopt a conservative approach in line with Dick and Grischenko (2017).