The ontogeny, palaeoecology and palaeogeographical inference of the ostracod Roundstonia globulifera

Abstract

The discovery of an abundant monospecific population of Roundstonia globulifera (Brady) 1868 from an early Flandrian (9000–8500 B.P.) Dublin Bay mud horizon at ‐ 18 m Ordnance Datum has resulted in an ontogenetic analysis of the ostracod. Data on size, shape and morphological development through eight growth‐stages are presented. It occurs with a monospecific population of the foraminifer Elphidium clavatum subclavatum Gudina, the ecology of which is known. From this, and sedimentological data, it is inferred that the assemblages lived in shallow, muddy estuarine channels. Information from other parts of the Irish Sea provides evidence of the course of the Flandrian transgression. It is proposed that early in Boreal times, water masses invading from the north and south, were separated by a barrier south of Dublin until 8500 B.P.