The Rigelj Formation is a new lithostratigraphic unit of the Lower Permian Rattendorf Group in the Karavanke Mountains. The Formation is up to 105 m thick and mainly composed of siliciclastic and ...fossiliferous carbonate sediments that are entirely of shallow-marine setting. Conglomerates are interpreted as shoreface deposits, sandstones as deposits of the upper to lower shoreface, and fossiliferous siltstones as offshore deposits. Fossiliferous limestones were deposited in a shallow, open-marine shelf environment of moderate to low energy (wackestone, floatstone) and strong water turbulence (packstone, rudstone). The siliciclastic and carbonate lithotypes form some well-developed backstepping cycles starting with conglomerates, overlain by sandstones, siltstones and fossiliferous limestones that formed in an open shelf environment without siliciclastic influx. Similar sedimentary cycles are developed in the Grenzland Formation of the Carnic Alps.
The fusulinid fauna indicates that the Rigelj Formation ranges in age from the late Asselian to the middle Sakmarian. In the western Karavanke Mountains and near Trögern, the Lower Permian lithostratigraphic succession is very similar to the succession in the Carnic Alps with Tarvis Breccia resting on the Trogkofel Limestone and the Goggau Limestone. Unlike this, in the central part of the Karavanke Mountains (Dovžanova Soteska–Mt. Pleschiwetz/Plešivec area) the Rigelj Formation is erosively overlain by the Tarvis Breccia. The stronger diversification of the sedimentary environments within the Karavanke-Carnic Alps in the Lower Permian after the uniform sedimentation in the Upper Carboniferous can be attributed to block-faulting.
The proposal of the new genus is based on Sloveniaxon asseliensis sp. nov. from the late Early Asselian of the Dovžanova Soteska section NNE of Tržič (Karavanke Mts.), in a Cyathaxonia facies ...assemblage with Cyathaxonia and Lophophyllidium. Together with Variaxon Fedorowski, 2010, the taxon is classified as Variaxoninae Fedorowski, 2010 of Antiphyllidae Iljina, 1970 (suborder Zaphrentoidina Schouppé & Stacul, 1959), descending from Rotiphyllum Hudson, 1942. Sloveniaxon was widely distributed in Eurasia (Spain, Hungary, Russia, Ukraine, Iran, Timor, China) during Late Bashkirian, Moscovian, Asselian, Sakmarian?, Late Artinskian, Capitanian, Dzhulfian? times; there it had been mostly misidentified as really quite homoeomorphic Cyathaxonia Michelin, 1847 or Cyathocarinia Soshkina, 1928 (suborder Cyathaxoniina Spasskiy, 1977). The diagnostic difference is a true aseptal columella (Cyathaxoniinae Milne-Edwards & Haime, 1850) against a massive septal pseudocolumella (Variaxoninae), best visible in cross sections of the calice. For unambiguous identification, often neglected studies of the calicular phase are demanded to see the axial boss in statu nascendi without later stereoplasmatic thickening and diagenetic recrystallisations.Future modern revisions (including intensive serial sectioning) should verify the proposed transfer of the following previous species into Sloveniaxon: Cyathaxonia (Cyathocarinia) multituberculata Soshkina, 1928, Cyathaxonia angularis Fomichev, 1953, Cyathaxonia archangelskyi Fomichev, 1953, Cyathaxonia lomonossovi Fomichev, 1953, Cyathocarinia crassata Guo, 1980, Cyathaxonia degrootae Rodríguez, 1984, Cyathaxonia pinguis Rodríguez & Kullmann, 1999, Cyathaxonia sp.n.B, Rodríguez & Kullmann, 1999.
