Syracosphaera halldalii and Calyptrolithina divergens var. tuberosa life-cycle association and relevant taxonomic remarks Maria V. Triantaphyllou 1 , Margarita D. Dimiza 1 , Michael D. Dermitzakis 1 University of Athens, Faculty of Geology, Department of Historical Geology-Paleontology, Panepistimiopolis, 15784, Athens, Greece email: mtriant@geol.uoa.gr ABSTRACT: Water samples were collected for coccolithophore analysis at coastal environments, in August 2002, from 7 stations in the Gulf of Kastro (Andros Island, middle Aegean Sea, Eastern Mediterranean). The studies on coccolithophore regional dynamics in the middle Aegean Sea coastal environments have revealed a unique heterococcolith–holococcolith combination coccosphere indicating a life-cycle association of the taxa Syracosphaera halldalii in Gaarder and Hasle 1971 ex Jordan and Green 1994 and Calyptrolithina divergens var. tuberosa (Heimdal 1980) Jordan et al. 1993. Consequently their systematic taxonomy is emended and the name Syracosphaera halldalii is considered as the appropriate one for the well-established association. INTRODUCTION Coccolithophores form a major component of the marine nannoplankton and are one of the main open ocean primary pro- ducers, which at least at some points in their life cycle, produce and bear minute calcium carbonate plates called coccoliths. Two structurally different types of coccoliths, heterococcoliths and holococcoliths, formed by different types of biomineral- ization, are recognizable (Young et al. 1999). Several cocco- lithophores have been proven from culture studies to have complex life-cycles involving alternate production of holo- and heterococcoliths in the haploid and diploid phases (Houdan et al. 2004). Rare observations from natural populations of combi- nation coccospheres have been interpreted as representing the moment of life-cycle transition, greatly extending the range of documented cases of such life-cycles (e.g. Lecal-Schlauder 1961; Kleijne 1991; Cros et al. 2000; Cortes 2000; Geisen et al. 2002; Cros and Fortuño 2002; Young et al. 2003). Nonetheless for the vast majority of extant coccolithophores the life-cycle is unknown and so there is an urgent need for more observations (Jordan et al. 2004). micropaleontology, vol. 50, supplement no. 1, pp. 121-126, text-figure 1, plate 1, tables 1-2, 2004 121 TEXT-FIGURE 1 (a) Generalised pattern of the summer currents in the Aegean Sea during summer (based on Lacombe and Tchernia 1972). (b) Map of the study area (Andros Island). (c) Location of the sampled stations.