Vegetative and Reproductive Morphology of an Extinct Early Cretaceous Member of Platanaceae from the Braun’s Ranch Locality, Kansas, U.S.A.

Abstract

Early Cretaceous platanoid species are presented, based on observations of isolated organs from the Braun Ranch locality, Kansas, and the Yankee Hill I locality, Nebraska. Approximately 500 leaf specimens and 238 infructescence specimens have been studied in detail. The reproductive axis may contain up to 37 sessile, globose infructescences. Fruits are small achenes and lack dispersal hairs. The leaves are typically three-lobed, with basal or suprabasal actinodromous or palinactinodromous venation. Secondary venation is dominantly craspedodromous. Typically, one secondary vein extends into each tooth and is accompanied by tertiary or higher-order veins, which form a series of ascending loops. Tertiary veins are percurrent, with those in the axils of primary-primary and primary-secondary veins forming a V-shaped pattern. Conically inflated petiole bases are hollow and enclose axillary buds. Stipules are triangular and small and are observed only on immature leaves. The repeated and common co-occurrence of leaves and reproductive structures and their close association at a small clay pit in Cloud County, Kansas, indicates that they are organs from one plant species. This report provides new information on the early diversity of the Platanaceae in the fossil record during the Early Cretaceous.