Alterbidinium austrinum Roncaglia et Schioler, sp nov., a new dinoflagellate from the Conway Siltstone (Upper Cretaceous), southern Marlborough, New Zealand

The new dinoflagellate Alterbidinium austrinum Roncaglia et Schioler, sp. n ov. from the uppermost lower Haumurian (mid-upper Campanian) Isabelidinium korojonense Interval Zone in New Zealand, is a large, circumcavate, dorso-v entrally compressed, peridinioid cyst with subpentagonal outline. The peric yst bears two lateral and two or three antapical hems. One or two projectio ns/horns usually occur at the apex. The endocyst is thin-walled, subcircula r, and located centrally. The paratabulation is expressed by the paracingul um and the intercalary hexa 2a peri-archeopyle. Alterbidinium austrinum was encountered in a narrow stratigraphic interval in the Conway Siltstone, an d may be a potential stratigraphic marker. (C) 1999 Elsevier Science B.V. A ll rights reserved.