EARLY CRETACEOUS TETRADS, ZONASULCULATE POLLEN, AND WINTERACEAE. II. CLADISTIC ANALYSIS AND IMPLICATIONS

Comparisons with other fossil pollen types and the distribution of pollen characters in modern angiosperms support affinities of Early Cretaceous ulcerate tetrads ( Walkeripollis ) and zonasulculate pollen ( Afropollis, Schrankipollis ) with modern Winteraceae. Cladistic analysis of these fossils plus modern Winteraceae and Illiciales, which have been associated with each other, implies that Afropollis and Schrankipollis represent an extinct sister group of Walkeripollis, Winteraceae, and Illiciales, derived from a common ancestor before origin of the tetrad condition. The single tricolpate grains of Illiciales are derived from ulcerate tetrads, which helps explain their thin proximal exine and Garside's Rule aperture arrangement. These results imply that extinct relatives of Winteraceae and Illiciales were an important component of Early Cretaceous tropical floras and extended into Laurasia, and that the present austral temperate distribution of Winteraceae was attained later. They are consistent with recent suggestions that absence of vessels in Winteraceae is due to secondary loss.