- Copyright © 2017, SEPM (Society for Sedimentary Geology)
The first identification of Biplanispira in Armenia is of great interest due to the rarity of this genus outside of the Indo-Pacific bioprovince. In the Western Tethys, it had been recorded only from Spain. In the Urtsadzor section of Southwest Armenia, matrix-free specimens of pellatispirids are abundant, allowing a detailed study of their morphology. The aim of this work is therefore the morphological, systematic, and stratigraphic analysis of the genus Biplanispira. The Biplanispira specimens found in Armenia are identified as B. absurda, although they differ from type specimens from Borneo by smaller size of the primary chambers in second and third whorls, higher and more regular spire, larger pillars and development of spiral lateral chamberlets in subequatorial position. The same features are observed in most specimens of B. absurda described from Spain and permit the recognition of two subspecies: B. absurda absurda, distributed in the Indo-Pacific and B. absurda cataloniensis (Matsumaru 1999), found in Armenia and Spain. In Armenia, the stratigraphic range of Biplanispira is restricted to the Bartonian subzones SBZ18B-C in the shallow-water zonation and Priabonian zones E14 and NP19 in the planktonic zonations. The systematic position of pellatispirids between the families Calcarinidae and Nummulitidae is discussed, being closer to the former.