New species and evolution of the foraminiferal family Janischewskinidae in the middle–upper Mississippian of South China

Abstract

Rich foraminiferal assemblages from the Bama Platform in South China allow clarifying the systematics, composition, and biostratigraphy of the family Janischewskinidae. The family is comprised of four genera, Janischewskina, Cribrospira, Bibradya, and Parajanischewskina. The genera Rhodesinella and Groessensella are considered to be synonyms of Cribrospira and Bibradya, respectively, and some specimens of the genus Ugurus have been included under the genus Bibradya. Seven new species are described in this study: Cribrospira evoluta, C. paradenticulata, Bibradya primitiva, B. densicamerata, B. maxima, B. subita, and Parajanischewskina nautiliformis. The biostratigraphy of the Janischewskinidae in South China resembles that in the Russian Platform, i.e., primitive Cribrospira are first recorded from the Tulian, primitive Bibradya from the Aleksinian, evolved Cribrospira (e.g., C. panderi) and large Janischewskina species from the Mikhailovian, Parajanischewskina and Bibradya maxima from the Venevian, and some species from the base of the Serpukhovian (Tarusian), such as Janischewskina delicata, J. gibshmanae, Bibradya subita, and Parajanischewskina nautiliformis. On the other hand, Janischewskina adtarusia is only documented from the late Serpukhovian strata (Zapaltyubian).