Variation inGloborotalia puncticulata sphericomiozeafrom New Zealand (Foraminiferida, Neogene)

Abstract

The shape of shell profiles (spiral, axial) of Globorotalia puncticulata sphericomiozea from the type locality and from two early populations (also from Kapitean Stage, dose to Miocene-Pliocene boundary) is studied using Fourier amplitudes. Sample distributions for the major harmonics (2–4) and projections of 10 harmonics on to principal component axes are unimodal. There is a continuous spectrum of form (axial profile) from conical shells with keel at the angular periphery (G. conomiozea morphotype) to regularly curved shells that anticipate the shape of G. puncticulata puncticulata. Globorotalia puncticulata sphericomiozea seems to represent a stage in the transition from truncatuline form (G. conomiozea populations) to turborotaline form (G. puncticulata puncticulata and its descendant, G. inflata).