Chaperia lata sp. nov.

(Fig. 14)

Etymology. Latin latus, broad, alluding to the distinctively broad opesia.

Material examined. Holotype: NIWA 134521, Stn 9680, NNE of Te Rerenga Wairua / Cape Reinga, Northland, North Island, 34.3600° S, 172.6970° E, 46 m, 26 January 1999 (Cruise ID 3054) on a petrosiid sponge. Paratypes: NIWA 92676, Stn TAN1105/42, Middlesex Bank, 33.9505° S, 171.7725° E ‒ 33.9538° S, 177.7725° E, 92‒96 m, 28 March 2011 (Ocean Survey 2020); NIWA 161238, Stn Z19325, NE of Great Island (Manawatāwhi), Three Kings Islands, 34.1184° S, 172.2124° E ‒ 34.1202° S, 172.2074° E, 241‒250 m, 17 March 2019, encrusting branching stems of bryozoan Galeopsis polyporus; NIWA 173215, same substratum and data as holotype; NIWA 121209, Stn TAN0906/25, NE of Matapouri, Northland, 35.5525° S, 174.5525° E ‒ 35.5483° S, 174.5528° E, 57 m, 5 July 2009 (Ocean Survey 2020, Site Z8). Other material: NIWA 173216, small ancestrulate colony detached from stem of bryozoan Menipea vectifera, same data as holotype.

Description. Colony encrusting, unilaminar, multiserial; up to 18 mm length, encrusting firm sponge and bryozoan substrata.

Zooids subhexagonal, generally wider than long but proportions variable, margins straight or slightly curved, distal rim arcuate; widest about midlength, with distinct interzooidal boundaries in which very thin gymnocyst may be present. Cryptocystal frontal wall extensive, lightly and unevenly granular, proximally slightly depressed, sloping upwards to smooth, narrow, rounded, curving rim around proximal margin of opesia. ZL 373‒823 (550), ZW 397‒777 (622), n = 30. Mean ZL:ZW ratio 0.88.

Opesia half or less of zooid length, always wider than long, the discrete smooth margin biconvex in the middle, hence arched distally and with a moderately deep sinus-like proximal margin. Frontal rims of occlusor laminae curving so as to converge distally as a continuous arch. Occlusor muscle recesses tapering and pointed distally, wider proximally. OpL 148‒264 (210), OpW 206‒329 (277), n = 30. Mean OpL:ZL ratio 0.38.

Oral spines in zone of astogenetic repetition 4‒6 in single series around distal third, or less, of opesia, the mid-distal 1‒2 spine bases smallest; 6 spines predominant (55%), with 5 spines having 43% frequency. All spine bases set within narrow gymnocystal strip that continues interzooidally. Spines disposed more or less vertically, straight or slightly curving, the distomedial spines thinner and shorter than others; longest spines up to 730 μm. Spine arc bordering 1‒71% of opesia length (mean 28%, n = 26).

Ooecium vestigial, strongly crescentic, widest medially where a short round extension slopes distally, containing a conspicuous pore; proximolateral tips of ooecium pointed. Ooecium subjacent to 5‒6 spine bases. OoW 214‒324 (269), n = 10.

Mural septular pores distributed across much of lateral walls, which are interior walls; interior face showing pores distributed in a linear row high on wall and a similar row low on the wall, with additional pores less ordered between these rows. Outer face showing pores in upper half of wall set in small concavities; pores in lower half set in much larger concavities. Entire surface of outer face of each lateral wall with scattered spinules that are denser high on wall. A narrow panel of interior wall bounded by a pair of fine gymnocystal strips occurs mid-distally, with a vertical series of recessed pores (below ooecial pore when present).

Ancestrula subrounded, a little longer than wide, bordered by 9 almost equally distributed spine bases, the frontal edge of the gymnocyst concave between each spine pair, conferring a scalloped appearance to the ancestrular frontal perimeter. Opesia proportionally large, being a little longer than the sparsely tubercular cryptocyst. AnL 385, AnW 348, AnOpL 153, AnOpW 197, n = 1.

Ancestrula surrounded by 7 autozooids, comprising a mid-distal and 2 distolateral daughter zooids, 2 lateroproximal and 2 proximal zooids.

Remarks. Chaperia lata sp. nov. is unique among extant New Zealand Chaperia species for its biconvex eye-shaped opesiae and zooids that have a higher average width than congeners. The holotype occurred on dried sponge fragments, which, based on SEM examination, are most closely comparable to Petrosia australis Bergquist & Warne (Haplosclerida, Petrosiidae), first described from Three Kings area and well known around northern New Zealand and offshore banks. The oxeas are in the right size range and the skeleton is characteristic of petrosiids.

Distribution. Endemic; a distinctively northern New Zealand species, ranging from 33.9‒ 35.5° S at depths of 46‒250 m on sponges and bryozoans.