MORPHOLOGIC VARIATION IN THE BENTHIC FORAMINIFERA SPECIES LENTICULINA JUGOSUS CUSHMAN AND THOMAS

In order to establish a clear taxonomic system, an understanding of the degree of morphologic variation is essential. The benthic foraminifera species Lenticulina jugosus Cushman and Thomas is an uncommon but distincitve species in the Eocene and Oligocene sediments of the Gulf Coastal Region. This species has been described as having two distinct morphologies, a larger microspheric form, and a small meglospheric form. The presence of two distinct forms allows for analysis of the limits of variation and species identification. Specimens from the Upper Eocene and Lower Oligocene of Alabama and Mississipi were examined using a series of morphologic characters. Analysis of L. jugosus was conducted using SEM images of specimens in two orientations to allow measurement of the maximum number of features. A series of measurements where taken including: maximum test length, test width, test thickness, apertural face height apertural face width, number of chambers in last whorl and initial chamber width in the meglospheric form. Analysis of the measurements indicate a large degree of variation in both the meglospheric and microspheric forms. This result indicates that variation within this and other benthic foraminifera species complicates the recognition of species and requires careful description and definition of morphologic variation in species definition.