A flower from the early Cenomanian of northeastern Maryland, Cecilanthus polymerus gen. et sp. nov., is described using SEM and synchrotron X-ray microtomography. The flower has >20 strap-shaped tepals, ca. 50 spathulate stamens with embedded adaxial pollen sacs and possibly H-valvate dehiscence, and ca. 100 more or less plicate carpels. Floral phyllotaxis is whorled, with >10 parts per whorl, but slightly irregular. Pollen and ovules are not preserved, but locule shape suggests the carpels are uniovulate. Similar characters occur in extant Magnoliales and the basal ANITA grade, but never in combination. In an attempt to resolve these ambiguities, we performed morphological phylogenetic analyses with the arrangement of extant taxa constrained to trees based primarily on molecular data. With anther dehiscence and ovule number treated as unknown, Cecilanthus has several most parsimonious positions: nested in Nymphaeales, nested in Magnoliales, sister to Laurales, and sister to Chloranthaceae. However, scoring anther dehiscence as H-valvate and ovule number as one increases support for a position in Magnoliales. Cecilanthus demonstrates that the early radiation of angiosperms produced floral morphotypes unlike those in any surviving taxa, and it illustrates the value of characters such as pollen morphology and seed anatomy for phylogenetic placement of floral mesofossils.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
