SHELL ARCHITECTURE IN THE LATE CRETACEOUS FORAMINIFERAL SUBFAMILY CLYPEORBINAE SIGAL, 1952

The shell architecture of the genera Sirtina , Neumannites , Vanderbeekia and Clypeorbis is analyzed in detail, and the genera are assigned here to the subfamily Clypeorbinae Sigal, 1952. The Clypeorbinae, which lacks folia and any kind of plates in its spiral chambers, must be removed from the rotaliids. The subfamily represents a Tethyan group of Late Cretaceous, spiral, benthic foraminifera that tended to become orbitoidiform in parallel with a Caribbean group, consisting of Sulcoperculina , Vaughanina , Pseudorbitoides and cohorts (Pseudorbitoidinae Rutten, 1935, including Sulcoperculina ), all of which developed supplemental skeletons with extensive canal systems. The transition from spiral to cyclical, orbitoidiform species within the Clypeorbinae was accompanied by the development of (primarily dorsal) lateral chamberlets. This development is interpreted as a transformation of elongate alar prolongations of involute spiral chambers into lateral chamberlet cycles that are arranged in a chessboard pattern. The functional significance of the dorsal superstructure as a greenhouse for symbionts is considered as driving the frequent and repetitive trend to acquire orbitoidiform shell architecture. The structural analysis for the taxonomy in this work resulted in validation of the genus Neumannites Rahaghi, 1976, attribution of the species Iranites ornatus Rahaghi, 1976 to the genus Sirtina and introduction of a new species Vanderbeekia catalana .