Eurystomella biperforata, Gordon, Dennis P., Mawatari, Shunsuke F. & Kajihara, Hiroshi, 2002

Gordon, Dennis P., Mawatari, Shunsuke F. & Kajihara, Hiroshi, 2002, New taxa of Japanese and New Zealand Eurystomellidae (Phylum Bryozoa) and their phylogenetic relationships, Zoological Journal of the Linnean Society 136 (2), pp. 199-216 : 203

EURYSTOMELLA BIPERFORATA SP. NOV.

( FIG. 1C–E )

Eurystomella foraminigera: Brown 1952: 286 (part), fig. 216 (not fig. 215); Powell 1967: 310 (part), fig. 66a–b; Uttley & Bullivant 1972: 47; Gordon 1984: 65 (part), pl. 21f; 1989: 17 (part), pl. 4 a–c.

Material examined

Holotype: NZOI H-748, from NZOI Stn B 230, 46°40.0¢S, 168°02.5¢E, 26 m, Foveaux Strait , New Zealand.

Paratype: NZOI P-1217, from NZOI Stn Z 9697, 34°21.06¢S, 172°42.53¢E, 57 m, Spirits Bay , New Zealand .

Other material: NZOI Stns B220, B221, B224, B230, B235, D273, K837, Z9671, Z9677, Z9678, Z9687, Z9695, Z9697, Z9700, Z9708, Z9710, Z9716. Chatham Islands 1954 Expedition Stn 24, 69 m (see Uttley & Bullivant, 1972) .

Description

Form of colony and colony colour as in E. foraminigera . Autozooids contiguous, quincuncially arranged, 0.37–0.74 mm long (0.53 ± 0.10 mm) and 0.28–0.53 mm wide (0.36 ± 0.079 mm). Gymnocystal frontal shield scarcely elevated, perforated by 2, exceptionally 1 (or 3 in proximally elongated zooids), large oval to circular foramina; if oval, often with the long axes directed obliquely away from each other; shield surface smooth proximal to foramina. Orifice as in E. foraminigera , the proximolateral corners also having a slight excavation of the gymnocystal surface beyond the indentations of the orifice. No peristome, umbones, spines, or avicularia; low bosses may be on the frontal shield between the orifice and foramina in some zooids. Maternal zooids and kenozooids as in E. foraminigera , including the size of the kenozooid and its foramen, except that the maternal orifice is more consistently broader (0.23 mm wide at the proximal margin) than that of other zooids (0.16–0.19 mm). Zooids likewise communicating by distal and lateral pore-chambers and the ancestrula (0.38 ¥ 0.34 mm) has the same form.

Etymology

From bi - (L) two, and perforatus (L) bored through, alluding to the two perforations of the kenozooid distal to the maternal zooid.

Remarks

Eurystomella biperforata is so similar to E. foraminigera that it must be asked if the number of gymnocystal foramina is a sufficiently reliable character for segregating a new species. It is now clear, from the examination of many colonies of both species, that foramen number is indeed consistent, but, beyond this externally obvious character, there is an important internal feature as well. Whereas the interior of the frontal shield in E. foraminigera is uniformly smooth and featureless (apart from the foramina), that of E. biperforata has an abrupt demarcation in its angle of slope, creating a line that curves around the proximal margins of the foramina. Additionally, in some zooids, the ascus roof is partially calcified.

Distribution

Eurystomella biperforata is endemic to New Zealand, where it ranges from 30°15¢S (Macauley Island, Kermadec Ridge) to 46°30¢S (Foveaux Strait) at 26–125 m depth. In the field, live colonies of E. biperforata are probably indistinguishable from those of E. foraminigera .

Figures

Figure 1. A, B, Eurystomella foraminigera. Greta Point, Wellington, intertidal. A, group of zooids, ¥65. B, suboral rim, showing triradiate suture, ¥803. C-E, Eurystomella biperforata sp. nov. C,E, NZOI Stn Z9700. C, group of autozooids, ¥53. D, NZOI Stn Z9677, maternal zooid with distal foraminate kenozooid, ¥95. E, rare zooid with a single foramen, ¥163. F, Eurystomella aupouria sp. nov. NZOI Stn Z9716, ¥63.