A mid‐Cretaceous monocot flower from the Dakota Sandstone of Kansas and its potential implications for the fossil record of palms

PREMISE: Although the megafossil flora of the upper Albian-lower Cenomanian Dakota Formation in Kansas is well known for angiosperms, monocots have not been reported previously. METHODS: A mesofossil flower was discovered by X-ray analysis of a specimen collected more than a century ago from the Dakota Sandstone of central Kansas. A mid-Cretaceous (ca. 100 Ma) age is inferred from its stratigraphic provenance close to the Albian-Cenomanian boundary. Successive virtual transverse and longitudinal sections and a three-dimensional rendering generated from micro-CT scanning facilitate recognition of the floral parts and their organization. RESULTS: The flower is about 1.5 mm high and 1.2 mm in diameter, is actinomorphic and borne on a slender pedicel, and possesses three free sepals alternating with three free, coriaceous petals and six stamens in two whorls, one opposite the petals, and the other opposite the sepals. The gynoecium consists of three apocarpous, flask-shaped carpels, each with a ventral apical stigmatic groove. CONCLUSIONS: This flower, which we name Tomlinsoniella pedicellata gen. et sp. nov., constitutes the first mesofossil evidence for monocots in the Dakota Formation. Importantly, it also appears to be the earliest unequivocal fossil evidence for the appearance of the trimerous-pentacyclic floral plan typical of many monocots. Among extant monocots, this combination of characters is most consistent with the coryphoid palm lineage, although the fossil could also belong to an extinct monocot clade. If correct, this represents the earliest known mesofossil record of a commelinid monocot.