Seed plant phylogeny is evaluated using a data set of 46 terminals (taxa) and 103 morphological and anatomical characters. Cladistic analyses using the criterion of parsimony were performed on the complete data set as well as on subsets of the data, e.g., excluding fossils and/or combining various complex taxa into single terminals. The results support the placement of the cycads as the sister group of a monophyletic group that includes several fossil "seed ferns" as well as extant Ginkgo, conifers, gnetopsids, and angiosperms. When fossils were included, Bennettitales (cycadeoids) were part of an "anthophyte" clade that included gnetopsids and angiosperms. Pentoxylon was a sister taxon to the core anthophyte clade, in some, but not all, of the most parsimonious trees. Caytonia was not found to be closely associated with the anthophyte clade, but instead was often associated as a sister taxon of the glossoptends, and these two taxa were consistently outside of the Gin&go-conifer-anthophyte clade. In all most parsimonious trees for all analyses, Ephedra was to the outside of a clade that included all angiosperm taxa, Gnetum, and Welwitscnia, thus rendering the traditional gnetopsid clade paraphyletic. New information is provided on the morphology of Caytonia and some previous interpretations of homology of the caytonian "cupule" are rejected. The effects of sampling, compartmentalization, and polymorphism are explored in these data, snowing how different results may be obtained when polymorphic or "summary" terminals are used. The need for more work on gnetopsids and fossil taxa is suggested.

AlSSTKACT have been discovered within the past 15 to 20 years. These floras are particularly abundant in I p per Cretaceous sediments and have been reported from widely sepaiate geographic regions in the Northern Hemisphere. The first comprehensive studies were based on European material, and rich Lite Cretaceous floras are known from Cenomanian to Maastrichtian strata of the Czech Republic. Germanv. \ustria, the Netherlands, Portugal, and S\eden (

A molecular dating of the phylogenetically basal eudicots (Ranunculales, Proteales, Sabiales, Buxales and Trochodendrales sensu Angiosperm Phylogeny Group II) has been performed using several fossils as minimum age constraints. All rbcL sequences available in GenBank were sampled for the taxa in focus. Dating was performed using penalized likelihood, and results were compared with nonparametric rate smoothing. Fourteen eudicot fossils, all with a Cretaceous record, were included in this study for age constraints. Nine of these are assigned to basal eudicots and the remaining five taxa represent core eudicots. Our study shows that the choice of methods and fossil constraints has a great impact on the age estimates, and that removing one single fossil change the results in the magnitude of tens of million years. The use of several fossil constraints increase the probability of approaching the true ages. Our results suggest a rapid diversification during the late Early Cretaceous, with all the lineages of basal eudicots emerging during the latest part of the Early Cretaceous. The age of Ranunculales was estimated to 120 my, Proteales to 119 my, Sabiales to 118 my, Buxales to 117 my, and Trochodendrales to 116 my.

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