A new subfamily classification of the Coskinolinidae Moullade, 1965, Middle Jurassic-Paleogene Larger Benthic Foraminifera

The Coskinolinidae are a family of Middle Jurassic to Paleogene, typically orbitoliniform, Larger Benthic Foraminifera (LBF) characterized by a pseudokeriothecal wall structure. The type genus, Coskinolina Stache, 1875, lacks an exoskeleton (i.e., beams, rafters), resulting in an undivided marginal chamber zone. However, other taxa within the family, such as the Upper Cretaceous Lepinoconus Cruz-Abad et al., 2017, or the Paleogene Coleiconus Hottinger & Drobne, 1980, are genera with vertical partitions (beams) that subdivide the marginal chamber zone. In the currently accepted classification of agglutinated benthic foraminifera, the nature of the exoskeleton is a criterion for distinction at subfamily level, e.g., Cyclamminidae Marie, 1941. Thus, here, the presence or absence of an exoskeleton in the marginal chamber lumen is treated as a criterion at the subfamily level within the classification of the Coskinolinidae, leading to a division into two subfamilies: the Coskinolininae Moullade, 1965 (lacking an exoskeleton), and the newly proposed Coleiconinae subfam. nov. (with an exoskeleton of vertical partitions), as exemplified by Coleiconus Hottinger & Drobne, 1980.