On the Classification of the Lepidocyclinidae (Foraminiferida) with Redescriptions of the Unrelated Paleocene Genera Actinosiphon and Orbitosiphon

Abstract

Morphological characters employed in the description and supraspecific classification of the Lepidocyclinidae are explained and discussed in the context of evolutionary development. The subfamily Helicolepidininae is redescribed, special emphasis being laid on the condition of the embryonic apparatus, the thickening of the spiral wall, and the presence or absence of principal auxiliary chambers. Polylepidina is redefined, with P. chiapasensis (Vaughan) as its type species, and referred to the Helicolepidininae along with Pseudolepidina. Lepidocyclina antillea Cushman is assigned to Eulinderina. The Palaeocene genera Actinosiphon and Orbitosiphon are redescribed and removed from the Lepidocyclinidae. One new family, the Actinosiphonidae, and one new species, Orbitosiphon praepunjabensis, are erected. The subgeneric classification of the Lepidocyclininae is reviewed, and its continuation justified on the basis of stratigraphic utility. Changes made during the last 25 years are considered, and three subgenera, Lepidocyclina (Lepidocyclina), L. (Eulepidina), and L. (Nephrolepidina), are discriminated on the nature and arrangement of their periembryonic chambers, in particular, the presence or absence of adauxiliary chambers. Two distinct groups of species are recognized within L. (Lepidocyclina) on the basis of equatorial chamber shape. The evolutionary history of the Lepidocyclinidae is discussed briefly, and a key provided for the identification of genera and subgenera. A glossary of morphological terms is appended.