The known occurrence of corals distinguished here in the new Family Krynkaphyllidae varies at the subfamily level. Those of the Subfamily Krynkaphyllinae subfam. nov. are so far almost unknown from outside of the Donets Basin. In contrast, those of the Subfamily Colligophyllinae subfam. nov. are common, possibly ranging from the lower Viséan Dorlodotia Salée, 1920, a potential ancestor of the family, to the Artinskian Lytvophyllum tschernovi Soshkina, 1925. They bear different generic names, but were all originally described as fasciculate colonial. A detailed study of Lytvophyllum dobroljubovae Vassilyuk, 1960, the type species of Colligophyllum gen. nov., challenges that recognition in that at least some of those taxa are solitary and gregarious and/or protocolonial. As such, solitary, protocolonial and, probably, fasciculate colonial habits are accepted in the Colligophyllinae subfam. nov., whereas the Krynkaphyllinae subfam. nov. contains only solitary taxa. The resemblance to the Suborder Lonsdaleiina Spasskiy, 1974 led to the analysis of families included in that suborder by Hill (1981) in the context of their relationship, or homeomorphy, to Krynkaphyllidae fam. nov. This question primarily concerns the Family Petalaxidae Fomichev, 1953; a relationship with the Family Geyerophyllidae Minato, 1955, is more distant, if one exists. The distinct, parallel stratigraphic successions of taxa within two subfamilies of the Krynkaphyllidae fam. nov. document their probably common roots and early divergence. However, a lack of robust data precludes an interpretation or treatment of those successions as phylogenetic. The absence of key stratigraphic and morphologic data meant that eastern Asiatic taxa have not been considered in these successions; however, morphological similarities allow for their tentative inclusion within the Krynkaphyllidae fam. nov. The following new taxa are introduced: Krynkaphyllidae fam. nov., Krynkaphyllinae subfam. nov., Colligophyllinae subfam. nov., Krynkaphyllum gen. nov., Colligophyllum gen. nov., Protokionophyllum feninoense sp. nov., Krynkaphyllum multiplexum sp. nov., Krynkaphyllum validum sp. nov., and three species of Protokionophyllum Vassilyuk in Aizenverg et al., 1983 left in open nomenclature.

The Family Kumpanophyllidae Fomichev, 1953, synonymised by Hill (1981) with the Family Aulophyllidae Dybowski, 1873, is emended and accepted as valid. The new concept of this family, based on both new collections and discussion on literature data, confirms the solitary growth form of its type genus Kumpanophyllum Fomichev, 1953. However, several fasciculate colonial taxa, so far assigned to various families, may belong to this family as well. The emended genus Kumpanophyllum forms a widely distributed taxon, present in Eastern and Western Europe and in Asia. Its Serpukhovian and Bashkirian occurrences in China vs Bashkirian occurrences in the Donets Basin and in Spain, may suggest its far-Asiatic origin, but none of the existing taxa can be suggested as ancestral for that genus. Thus, the suborder position of the Kumpanophyllidae remains unknown. Four new species: K. columellatum, K. decessum, K. levis, and K. praecox, three Kumpanophyllum species left in open nomenclature and one offsetting specimen, questionably assigned to the genus, are described.

The paper focuses on the taxonomic description of the lower Carboniferous (uppermost Tournaisian to middle Viséan) solitary rugose corals from bedded limestone and shale units in the Flett Formation in the Jackfish Gap (eastern Liard Range), northwestern Canada. The corals described herein include 12 species representing the genera Ankhelasma Sando, 1961, Bradyphyllum Grabau, 1928, Caninophyllum Lewis, 1929, Cyathaxonia Michelin, 1847, Ekvasophyllum Parks, 1951, Enniskillenia Kabakovich in Soshkina et al., 1962, Vesiculophyllum Easton, 1944 and Zaphrentites Hudson, 1941. Two of these species are new (Ankhelasma canadense sp. nov. and Ekvasophyllum variabilis sp. nov.) and 6 taxa are described in open nomenclature. The distribution and relative abundance of solitary Rugosa in Europe and the Liard Basin confirm the geographical proximity of those areas and the open marine communication between them during the early Carboniferous. It therefore represents an important contribution to the determination of the time of isolation of the western Laurussia shelf fauna from that of southeastern Laurussia, as well as the time of the possible emergence of species from southeastern Laurussia into the western Laurussia seas. Of particular importance here are cosmopolitan taxa and the timing of their disappearance from the fossil record.

A detailed analysis of the upper Viséan, Serpukhovian and Bashkirian Rugosa of the Donets Basin confirms their Mississippian/Pennsylvanian turnover during the Eumorphoceras / Homalophyllites–Hudsonoceras Zone, as postulated earlier (Fedorowski 1981a). The deterioration of rugose corals, globally diverse in time and space in the late Viséan and Serpukhovian, has resulted in the patchy distribution of survivors and newcomers, present in the Bashkirian. Difficulties in inter-basinal communication and the isolation of some sites have resulted in a different content of Bashkirian Rugosa in particular patches, with only rare genera in common. New data has made it possible to document the appearance of the first late Carboniferous genera in the Donets Basin as early as the lower Voznessenkian Horizon (= lower Chokierian Substage), i.e., close to the beginning of the Bashkirian Stage. The two stages of diversification, established in the Bashkirian rugose corals of the Donets Basin, cannot find their counterparts elsewhere. A palaeogeographic overview of the most important sites of diversified rugose corals documents the need to re-examine many taxa, which should be based on complete specimen studies. This and the precise placement of taxa in the modern stratigraphy must be done in order to make rugose corals globally comparable. Simple repetitions of names, commonly used in general summaries, is strongly misleading in both stratigraphic and palaeogeographic reconstructions.

A new Subfamily Dirimiinae of the Family Kumpanophyllidae Fomichev, 1953 is introduced on the basis of Dirimia gen. nov., which is represented by six new named species and three species left in open nomenclature. The new species are Dirimia multiplexa, D. similis, D. recessia, D. composita, D. extrema, D. nana, Dirimia sp. 1, Dirimia sp. 2 and Dirimia sp. 3. The progressing atrophy of the columnotheca, leading to its total reduction in extreme species, and the occurrence of an axial structure instead of a compact pseudocolumella established in these species are accepted as differences exceeding the genus level. All specimens assigned to this subfamily were derived from the same Limestone F1 of the Donets Basin, and mostly from the same locality. The reasons for their split into a relatively large number of species are: 1) an increased radiation typical for faunal turnover times; 2) a delay in the appearance of differentiated skeletal characters relative to the appearance of genetic differences large enough to characterise different species; 3) a bias in preservation of fossil remnants by comparison to living populations, amplified by biases in the collections available for study by comparison to the total number of specimens fossilised.