The Fossil Flora of the Winthrop Formation (Albian-Early Cretaceous) of Washington State, USA. Part II: Pinophytina

Abstract

ABSTRACT The Winthrop Flora is of middle to late Albian age (Early Cretaceous) and occurs in the Methow basin of north-central Washington State, USA. With an estimated diversity of more than 150 species, the Winthrop is the most diverse flora yet described from the Early Cretaceous of North America. This paper deals with the 38 species of gymnosperms or Pinophytina of the Winthrop Formation, consisting of three species of Pteridospermopsida, three of Cycadopsida, three of Ginkgoopsida, nine of Bennittopsida, 15 of conifers or Pinopsida, and five species whose assignment is uncertain below the level of the gymnosperms. We describe four new genera and 21 new species of Pinophytina. Overall, the gymnosperm component of the flora is concordant with that of other late Early Cretaceous floras of the Northern Hemisphere. However, several of its species are similar to those found in Jurassic sediments from Mexico and Central America and some of the cycadophytes and conifers have what we interpret as xeromorphic f...