Permian Fusulinid Rugososchwagerina (Xiaoxinzhaiella) from the Shan Plateau, Myanmar: Systematics and Paleogeography

Abstract

Eastern Myanmar is an indispensable part of the Cimmerian Continent with Gondwana provenance. Fusulinids from Eastern Myanmar remain poorly known despite their biochronological and paleogeographical significance. This paper describes Rugososchwagerina (Xiaoxinzhaiella) subrotunda sp. nov. and Chusenella quasidouvillei of Murgabian age (Middle Permian) from the Thitsipin Formation at the Pindaya in the Shan Plateau, Eastern Myanmar. Taxonomic analysis of this new collection and of Rugososchwagerina (s.l.) in the literature leads us to suppress Xiaoxinzhaiella Shi, Yang & Jin, 2005 as a subgenus of RugososchwagerinaMiklukho-Maklay, 1959. This subgenus is diagnosed with much tighter coiling and reduced septal folding in juvenarium as well as relatively smaller test diameter throughout the ontogeny, compared with Rugososchwagerina (s.s.) which is typified by R. yabeiSkinner & Wilde, 1966. Furthermore, our comprehensive review reveals that the known occurrences of R. (Xiaoxinzhaiella) are strictly confined within blocks that previously constituted the Cimmerian Continent during the Permian period, and they were even more widespread than Rugososchwagerina (s.s.) among these blocks. Therefore, the previous understanding that Rugososchwagerina (s.l.) is characteristic for the Middle Permian Cimmerian region can be refined. We propose that R. (Xiaoxinzhaiella) is more appropriate as the truly endemic foraminiferal index signifying Cimmerian affinity.