First occurrence of Czekanowskia (Gymnospermae, Czekanowskiales) in the United States

Abstract

The distinctive filiform leaf Czekanowskia has recently been recognized for the first time in the United States in the Late Jurassic Morrison Formation of the Colorado Plateau Region. In this region, the taxon is represented at two localities by the new species C. turneri sp. nov., and at two other localities by fragments which cannot be identified to the species level. The new species has amphistomatic filiform leaves, a thin (2–3 μm) delicate cuticle, and shallow stomatal pits that are only rarely protected by papillae, characters which suggest that it lived in a humid climate. Czekanowskia, which is known only from the Mesozoic of the Northern Hemisphere, occurs most commonly in Eurasian coal-bearing sequences thought to have been deposited under a humid temperate to tropical climate. The occurrence of Czekanowskia in the Morrison Formation indicates that at least the upper part of the unit, where the taxon occurs, was probably deposited in a similar climate.