Family Membraniporidae Busk, 1852

Diagnosis. Colony encrusting, sheet-like, unilamellar, or with erect, frondose, tubular or vincularian growths from an encrusting base. Zooids elongate-oval (peri-ancestrular) to mostly rectangular, the membranous frontal wall covering the entire opesia or there is an area of proximal gymnocyst. A proximal cryptocystal shelf, with or without granulations and/or denticles, variably developed or lacking altogether. No avicularia. Polypide with an intertentacular organ. Ovicells absent, oligolecithal eggs released to the sea where they develop into planktonic cyphonautes larvae. Ancestrula twinned, constituting a diagnostic apomorphy for the family (Taylor & Monks 1997).