On the status of the Triassic radiolarian family Hexapylomellidae Kozur and Mostler: Taxonomic consequences

Abstract

This article represents a structural, morphological, taxonomic and evolutionary study of the familiy Hexapylomellidae Kozur and Mostler and of some morphologically related taxa undertook on the base of some radiolarian faunas of Middle and early Late Triassic from several radiolarian-bearing samples from Oman, Romania, Bosnia-Hercegovina, but especially from the middle Carnian of the Elbistan area, Turkey. This study has demonstrated that the genus Hexapylomella Kozur and Mostler, in spite of its name, has only 4 pylomes, not 6 as originally mentioned, and an entactinarian structure similar to that of the families Hindeosphaeridae, Sepsagonidae, Muelleritortidae, and Nodotetrasphaeridae. Consequently, the diagnosis of the genus is emended. This structural unity has taxonomic consequences: since the family Hexapylomellidae, in spite of its incorrect definition, has priority over all the other families of the group, it replaces the family Hindeosphaeridae. The article studies in detail the internal structure of the genus Tetraporobrachia Kozur and Mostler and of other related genera and discusses the evolution and origin of these radiolarians during the Late Ladinian and Early and Middle Carnian and proposes a new systematics at subfamily level. The family Hexapylomellidae is redefined and divided into 3 subfamilies: Hexapylomellinae, Hindeosphaerinae and Muelleritortiinae. Two new genera (Praehexapylomella and Praecapnuchosphaera) and 13 new species are described.