Eostangeria Barthel (Extinct Cycadales) from the Paleogene of Western North America and Europe

Abstract

Fernlike leaflets from the Paleocene of Wyoming and Eocene of Oregon are recognized as cycad foliage based on diagnostic epidermal structure. The fossils conform to Eostangeria Barthel, an extinct genus based on Eocene foliage from Germany, and are described as a new species, Eostangeria pseudopteris Kvaček et Manchester. Eostangeria resembles the extant South African cycad Stangeria T. Moore (Stangeriaceae) in gross morphology (featherlike leaflets with dentate margin), but the fossil more closely resembles Zamiaceae in epidermal structure. Convergence in pinnule form and venation makes it difficult to distinguish Eostangeria from Allantodiopsis Knowlton et Maxon, a fern common in the Paleogene of North America, whose epidermal anatomy remains unknown. However, the cycad can be distinguished in well‐preserved specimens by the presence of interstitial fibers and secondary veins that occasionally fuse at the margin. The occurrence of Eostangeria in the Tertiary of both Europe and North America indicates that it may have spread across the North Atlantic region.