Olisthella mimica, Gordon, Dennis P. & Taylor, Paul D., 2017

Gordon, Dennis P. & Taylor, Paul D., 2017, Resolving the status of Pyriporoides and Daisyella (Bryozoa: Cheilostomata), with the systematics of some additional taxa of Calloporoidea having an ooecial heterozooid, Zootaxa 4242 (2), pp. 201-232 : 218

Olisthella mimica n. sp.

( Fig. 10 C–E)

Material examined. Holotype: NIWA 27764 , NIC Wellington, Stn TAN 0604 /116, 42.7968° S, 179.9863° E, 950– 1045 m, Graveyard Seamount complex, north-central Chatham Rise, 7 June 2006 . Other material: NIWA 98222 , NIC Wellington, Stn TAN 0104 /389, 42.7832° S, 179.9940° E – 42.7803° S, 179.9895° E, 870–1000 m, Scroll Seamount, Graveyard Seamount complex, 21 April 2001.

Etymology. Latin mimicus, imitative, alluding to the similarity of this species to O. occlusa n. sp.

Description. Colony unilaminar, weakly pluriserial, with zooids contiguous or slightly disjunct, maximum spread 2 mm, hence small and spot-like. Autozooids more or less elongate-oval to subpyriform [ZL 754–945 (825); ZW 478–645 (577)]. Gymnocyst encircling entire autozooid, generally narrow throughout but may be a little broader proximally or proximolaterally. Cryptocyst and opesia encircled by a continuous raised rim that is smooth or weakly granular [CrL 556–689 (623); CrW 389–522 (465)]; cryptocystal shelf present, but relatively narrow, almost flat where it borders the opesia, gently sloping towards opesia, barely attenuating in width until it reaches the orificial area, entirely smooth or with weak granulation just within the rim. Opesia more or less narrowly elongate-oval, generally slightly broader proximally but also virtually parallel-sided in some zooids [OpL 421–528 (469)]. Articulated pericryptocystal spines 10–15 in number, all of nearly equal thickness including the distalmost six spines bordering the orifice in an arcuate series; 2–8 additional spines on the surrounding gymnocyst, the maximum number of spines seen on any one zooid = 22. Avicularia, ooecia and ancestrula lacking.

Remarks. Olisthella mimica n. sp. resembles O. occlusa n. sp. in having a similar colony form (a mix of contiguous and slightly disjunct autozooids) and opesial shape, but differs in having half the total number of spines (12–22 vs 23–44) per autozooid, and a smoother, narrower cryptocyst. Occluding kenozooids have not yet been seen in O. mimica n. sp.

Distribution. Endemic to the New Zealand EEZ; known only from the Graveyard Seamounts at 870–1045 m, where it encrusts gravel-sized clasts.

Figures

FIGURE 10. Olisthella contigua n. gen., n. sp., holotype, NIWA 95601: A, colony; B, close-up of zooid at upper left in A. Olisthella mimica n. gen., n. sp. C, unregistered; D, E, holotype, NIWA 27764: C, disjunct zooids, each with sparse, tiny spinebases on the lateral gymnocyst; D, close-up of anterior end of a zooid; E, zooids with pericryptocystal and gymnocystal spines. Scalebars: A, 500 µm; B, 200 µm; C, E, 300 µm; D, 200 µm.