Olisthella, 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 : 214

Genus Olisthella n. gen.

Diagnosis. Colony encrusting, multiserial; autozooids arranged contiguously in quincunx, communicating via basal pore-chambers. Gymnocyst well developed to moderate, narrowest distally. Cryptocyst and opesia surrounded by a distinct raised rim, the cryptocystal shelf extensive to moderate, flat or gently sloping, attenuating laterally. Opesia longer than wide, weakly or not constricted, almost parallel-sided or a little broader distally or proximally, with the distal third occupied by the opercular flap. Articulated spines mostly pericryptocystal, with additional spines borne on the sloping part of the gymnocyst. Avicularia absent. Ooecium hyperstomial, acleithral, smooth with a proximally facing excavation; ooecial kenozooid generally wholly concealed. Kenozooidal chambers regularly occupying interzooidal and intrazooidal spaces. Ancestrula like later zooids.

Type species. Olisthella occlusa n. sp.

Etymology. Latinised Greek, olisthos, slipperiness, plus - ella, a common bryozoan suffix, alluding to the ‘slippery’ morphological characters by which the genus is separated from Pyriporoides (see Discussion); gender feminine.

Remarks. This new genus shares some zooidal characters with Pyriporoides (see species descriptions) but is distinguished from it chiefly by having contiguous autozooids in quincunx with weakly constricted opesiae and smooth calcification bordering the opesia. The ooecial kenozooid is wholly concealed from frontal view, but this is also the case in two species of Pyriporoides . Other than the type species, four other New Zealand species are assigned to the genus, viz Olisthella mimica n. sp., Olisthella contigua n. sp., Olisthella plana n. sp., and the Eocene species Olisthella alma n. sp.; thus Olisthella , n. gen. is nominally endemic to the New Zealand EEZ.