Revised diagnosis. Colony encrusting, comprising branching uniserial runners. Autozooids more or less claviform, budded from small basal pore-chambers, with short or long caudae and extensive gymnocyst. Cryptocyst and opesia surrounded by a distinct raised rim, the cryptocystal shelf well developed, flat or gently sloping, attenuating laterally to opesial constrictions. Opesia longer than wide, typically constricted, with the distal part occupied by the opercular flap. Articulated spines perioral or pericryptocystal, with often additional spines borne on the sloping part of the gymnocyst. Avicularia rare, sometimes replacing the ooecial kenozooid or interpolated in a zooidal series. Ooecium hyperstomial, acleithral, smooth with a median suture or small proximofrontal excavation (longitudinal, triangular or transverse) that may be associated with a carina. Ooecial kenozooid generally protruding distally, with small opesial foramen surrounded by granular cryptocyst. Ancestrula resembling later zooids but rounded proximally, i.e. non-caudate. Occasional interzooidal kenozooids present, with a central opesial foramen.
Type species. Membranipora uniserialis Waters, 1904, by original designation.
Remarks. With the discovery of additional new taxa, described herein, Pyriporoides is now deemed to include seven species, allowing a fuller diagnosis of the genus. In chronological order of their naming, the species are P. uniserialis (Waters, 1904), P. circularis (Gordon, 1989), Pyriporoides libita (Gordon, 1989), Pyriporoides bathyalis (Rosso & Taylor, 2002), P. judyae Branch & Hayward, 2005, Pyriporoides aviculata n. sp. and Pyriporoides murdochi n. sp. Based on new understanding of the characters of Pyriporoides, the new combination Pyriporoides precocialis (Gordon, 1984) introduced by Gordon et al. (2009) is rejected; this species belongs to a new genus that will be described elsewhere. Pyriporoides is mainly austral in distribution, ranging from the southern Indian Ocean (600–775 m) and subantarctic New Zealand (887–1750 m) to West Antarctica (93–623 m). The sole exception is P. bathyalis, found in Icelandic waters and north of Scotland (740–1200 m).