Format: ORAL

Mario Coiro1, James A. Doyle2, Andrs Elgorriaga3, Leyla J. Seyfullah1

1 University of Vienna, Vienna, Austria 2 University of California, Davis, USA 3 University of Kansas, Lawrence, USA

Recent discoveries of new fossil taxa, improved data on poorly known fossils, and major reinterpretations of the morphology of several key taxa have potential to strengthen or refute previous hypotheses on seed plant phylogeny. To test the impact of these developments, we have amassed a new data set including Doylea (Cretaceous, recently assigned to the mainly Triassic seed fern order Umkomasiales, = corystosperms), Petriellaea (Triassic), and Protoephedrites (Cretaceous) and substantially redefined many previously used characters. We have revised the scoring of glossopterids in light of evidence that the ovule-bearing structures are axillary cladodes with ovules on the surface facing the subtending leaf and have rescored Bennettitales based on evidence that the ovules are borne on simple sporophylls and lack a cupule, while we interpret Doylea as having compound strobili with axillary fertile short shoots bearing ovules enveloped by lobes of the short shoot. Preliminary analyses associate glossopterids with coniferophytes rather than angiosperms, Doylea with conifers rather than corystosperms, Protoephedrites with Gnetales, and Petriellaea and Caytonia with angiosperms. The positions of Bennettitales and Pentoxylon are particularly unstable, presumably due in part to the uncertain morphological homologies of their reproductive structures. These results are consistent across different methods (parsimony, maximum likelihood, Bayesian inference) and models for character evolution. They may favor origin of the angiosperm leaf by webbing of a pinnately compound or lobed leaf, rather than differentiation of vein orders in a simple taeniopterid- or glossopterid-type leaf, and derivation of the carpel from a megasporophyll with pinnately borne cupules (bitegmic ovule homologs), rather than a leaf plus an axillary cupule-bearing branch.