Sprecher
Beschreibung
Discoveries of new fossil taxa, improved data on known fossils, and reinterpretations of the morphology of key taxa have challenged previous hypotheses on seed plant phylogeny and the origin of angiosperms. To test the impact of these developments, we amassed a data set with 10 new taxa, including Doyleales (Cretaceous, some originally assigned to the Triassic "seed fern" order Corystospermales), two Mesozoic conifer taxa with multiveined leaves, the cupulate "seed ferns" Petriellaea (Triassic) and Ktalenia (Cretaceous), and the Cretaceous compound strobilus Protoephedrites, plus several new and redefined characters. We rescored ovulate structures of glossopterids as cladodes with ovules on the side facing a subtending leaf, ovules of Bennettitales as lacking a cupule and borne on simple megasporophylls, and cones of Doyleales as compound strobili with bracts and lobed cone scales (fertile short shoots). We analyzed the data with both parsimony and Bayesian methods, with and without molecular constraint trees.
All our analyses associate Doyleales with conifers with multiveined leaves, Protoephedrites with extant Gnetales, and Ktalenia, Petriellaea, and Caytonia with angiosperms. The positions of glossopterids, Pentoxylon, and Bennettitales vary in parsimony analyses, but in Bayesian analyses Pentoxylon is linked with glossopterids and Bennettitales with gnetophytes. These results may favor origin of the angiosperm leaf by webbing of a pinnately compound leaf, rather than differentiation of vein orders in a taeniopterid or glossopterid leaf, and derivation of the carpel from a megasporophyll with pinnately borne cupules (homologous with bitegmic ovules), rather than a leaf plus an axillary cupule-bearing branch.