Integrating Cretaceous Fossils into the Phylogeny of Living Angiosperms: Fossil Magnoliales and Their Evolutionary Implications
James A. Doyle, Peter K. Endress
Abstract
Premise of research. In a 2010 phylogenetic study of Early Cretaceous angiosperms, we confirmed that Endressinia (Aptian) and Archaeanthus (Albian) belong to the magnoliid order Magnoliales, but since then several relevant new fossils and new data on characters have been reported. Here we analyze nine putatively magnolialean fossils, including four from the first half of the Late Cretaceous.Methodology. We evaluated relationships by parsimony analysis of a substantially revised morphological dataset of living and fossil angiosperms, with the arrangement of living taxa constrained to backbone trees based primarily on molecular data.Pivotal results. A study emphasizing fruit anatomy linked Archaeanthus with Liriodendron, but with our dataset the relationships among Archaeanthus, Liriodendron, and Magnolioideae remains unresolved. Endressinia and Schenkeriphyllum are probably sister to Magnoliaceae, rather than associated with Degeneria, Galbulimima, Eupomatia, and Annonaceae, as previously inferred for Endressinia. The Coniacian flower Futabanthus is probably nested within Annonaceae, but the Cenomanian flower Pecinovia is not related to the family. Aptian–Albian fruits and seeds named Serialis and Riaselis may be related to either Austrobaileyales or Magnoliales. The Turonian–Coniacian flower Cronquistiflora may belong in Magnoliales, possibly linked with Eupomatia, but Detrusandra is more likely austrobaileyalean. Affinities of the Cenomanian flower Cecilanthus remain ambiguous.Conclusions. Magnoliales, like other Magnoliidae, were actively diversifying alongside Chloranthaceae, eudicots, and monocots in the middle third of the Cretaceous. Endressinia and Schenkeriphyllum indicate that the line leading to Magnoliaceae originally had inner staminodes, and that the sheathing leaf base and dry fruit wall of Magnoliaceae originated before the loss of staminodes and elongation of the receptacle. The presence of Endressinia and Schenkeriphyllum in northeastern Brazil is consistent with an origin of the magnoliaceous line in Gondwana, and it implies that early Magnoliales could more easily adapt to dry tropical conditions than might be inferred from extant taxa.