Olisthella contigua Gordon & Taylor, 2017, n. sp.

Olisthella contigua n. sp.

(Figs 10 A, B, 12A)

Material examined. Holotype: NIWA 95601, NIC Wellington, Stn T 39, 49.5033° S, 178.7433’ E, 995 m, N of Antipodes Island, 14 March 1981. Paratype: NIWA 98223, colony adjacent to holotype on same substratum.

Etymology. Latin contiguus, neighbouring, near, alluding to the non-caudate, contiguous autozooids.

Description. Colonies infertile, comprising up to seven non-caudate contiguous autozooids, one of them regenerated from within another autozooidal cystid; maximum colony spread c. 1.3 mm, hence small and spot-like. Individual zooids broadly subpyriform [ZL 432–589 (482); ZW 322–445 (407)], apparently with three pairs of lateral septula as well as one mid-distal and one midproximal. Gymnocyst encircling entire autozooid, fairly extensive proximally, moderate to narrow laterally, narrowest distally, sloping to the substratum. Cryptocyst comprising a very broad, flat shelf surrounded by a raised rim that is potentially almost circular, except where it is produced outward around the distal margin of the opesia [CrL 278–394 (328); CrW 289–333 (317)]; surface granularity of cryptocyst appearing as irregular thin lineations trending more or less radially from the rim towards the opesia, the surface smooth bordering the opesia. Opesia longer than wide, its shape variable—it may be almost parallel-sided but it generally broadens distad; distal margin evenly rounded, proximal margin weakly rounded to straight or obliquely so [OpL 132–189 (162)]. Articulated pericryptocystal spines 10–13 in number; 6–7 border the orifice in an arcuate series, with the remainder distributed irregularly around the rim; the proximolateral orificial spines thickest; 7–11 additional spines on the gymnocyst proximally and laterally, and, in one other zooid where they are not obscured by debris, six others flank the oral spines, for a possible maximum total of 17 accessory gymnocystal spines. No avicularia. Ooecium not seen. Ancestrula subcircular, resembling later zooids, with six oral spines, three other pericryptocystal spines and no additional gymnocystal spines [AnL 344; AnW 300]. It buds the daughter zooid mid-distally (slightly obliquely so).

Remarks. Although this species is represented by only two small, non-ovicellate colonies, it is distinctive enough to be easily recognised should more material be found. In overall zooidal features O. contigua n. sp. most resembles P. circularis —the cryptocyst is broad and extensive, opesial shape is not very dissimilar, and beyond the pericryptocystal spines are several others borne on the flanks of the gymnocyst. The major difference is that the zooids are non-caudate and contiguous, raising the obvious question concerning the taxonomic/phylogenetic importance of the cauda and uniseriality (see Discussion).

Distribution. Endemic to the New Zealand EEZ, where it is known only from the vicinity of subantarctic Antipodes Island at 995 m depth. The two small colonies encrust rounded excavations in an angular pebble of vesicular basalt.