Early diverging asterids of the Late Cretaceous: Suciacarpa starrii gen. et sp. nov. and the initial radiation of Cornales

Abstract

Two permineralized cornalean fruits from the Campanian of the state of Washington in the northwestern United States were studied using the cellulose acetate peel technique. One specimen was reconstructed three-dimensionally using ImageJ software. Fruits are ellipsoidal and consist of valvate endocarps. Valves are restricted to the apical third of the endocarp. Endocarps are tetralocular and each locule is crescent-shaped in cross section. The valve tissue consists of isodiametric sclereids and secretory cavities. Septae are composed of transversely elongated sclereids and secretory cavities. In each septum there are roughly two rows of vascular bundles that extend the length of the fruit. There is one apically attached seed per locule. These fossil fruits display a unique mosaic of characters indicative of Cornaceae, Nyssaceae, Davidiaceae, and Mastixiaceae, but not conforming to any one of these extant families. Therefore, they are assigned to a new genus and species within Cornales, Suciacarpa starrii gen. et sp. nov. The novel combination of characters of Suciacarpa sheds light on the early evolution of Cornales and supports previous phylogenetic hypotheses.