Objective identification of Lepidocyclina (Foraminifera) species from the Eocene of Cuba based on growth-invariant morphometric characters

Abstract

Megalospheric specimens of Lepidocyclina from seven localities in western and central Cuba were morphometrically investigated using 11 growth-independent characters for equatorial sections of nepionts and 19 growth-independent and invariant characters describing equatorial sections of neanic chamberlets. This provides a complete geometric reconstruction of the equatorial morphology for lepidocyclinids. Specimens were objectively (to be precise, intersubjectively) classified by clustering and ordination methods resulting in four morphologically homogenous groups. These unprejudiced groups are then subjectively identified as Lepidocyclina macdonaldi, L. pustulosa, L. ariana and L. ocalana following the taxonomic rules and checked for significant differences. The D/P-ratio (deuteroconch/protoconch) separates L. ocalana (D/P ≥ 1) from L. pustulosa (D/P ≅ 1), L. macdonaldi and L. ariana (D/P < 1). The form of neanic chamberlets differentiates both L. macdonaldi and L. pustulosa possessing arcuate chamberlets from L. ariana and L. ocalana with spatulate chamberlets. The smaller sized characters isolate L. pustulosa from the other species. Lepidocyclina macdonaldi has the longest stratigraphical range occurring from ABZ 9 to ABZ 16 (American larger Benthic foraminifera Zonation). Lepidocyclina ariana is restricted to ABZ 12, while L. pustulosa and L. ocalana range from ABZ 13 to ABZ 16 and ABZ 15 to ABZ 16, respectively. An evolutionary trend could be detected in nepionts of L. macdonaldi starting from slightly smaller nepionts at the first appearance to significantly larger nepionts at the end of the Priabonian. Additionally, the arcuate chamberlets arranged in rows transform from not connected to connected. Differences within L. ocalana can be explained by environmental influences due to the palaeogeographical position of samples.