Published online by Cambridge University Press: 20 May 2016
Laminae of genera considered in this revision are sheets of planar, compact tissue (order Clathrodictyida) or a network formed by arms (colliculi) emerging from pillars (order Actinostromatida). Pillars, confined to a single interlaminar space, are simple rods, branch upwards, or have complex cross sections. The scope of Anostylostroma is limited to species with complexly upwardly branching pillars and simple planar laminae. Species with predominantly y- or v-shaped pillars are removed to Schistodictyon. Simplexodictyon is limited to species with double laminae formerly referred to Diplostroma. A new genus, Petrostroma (type species: Simplexodictyon simplex Nestor), is proposed for species with simple, planar laminae and rodlike pillars. The scope of Atelodictyon is restricted to species with planar, simple laminae resembling the type species and many species with laminae formed of colliculi previously placed in this genus are assigned to Aculatostroma. Other genera discussed include: Crumplestroma and Coenellostroma (both synonyms of Aculatostroma), Pseudoactinodictyon, Stelodictyon, Clathrodictyon, and Nexililamina and Coenostelodictyon (both synonyms of Schistodictyon).