title: Early Cretaceous Umkomasia from Mongolia: implications for homology of corystosperm cupules.
abstract: Corystosperms, a key extinct group of Late Permian to Early Cretaceous plants, are important for understanding seed plant phylogeny, including the evolution of the angiosperm carpel and anatropous bitegmic ovule. Here, we describe a new species of corystosperm seed-bearing organ, Umkomasia mongolica sp. nov., based on hundreds of three-dimensionally preserved mesofossils from the Early Cretaceous of Mongolia. Individual seed-bearing units of U. mongolica consist of a bract subtending an axis that bifurcates, with each fork (cupule stalk) bearing a cupule near the tip. Each cupule is formed by the strongly reflexed cupule stalk and two lateral flaps that partially enclose an erect seed. The seed is borne at, or close to, the tip of the reflexed cupule stalk, with the micropyle oriented towards the stalk base. The corystosperm cupule is generally interpreted as a modified leaf that bears a seed on its abaxial surface. However, U. mongolica suggests that an earlier interpretation, in which the seed is borne directly on an axis (shoot), is equally likely. The 'axial' interpretation suggests a possible relationship of corystosperms to Ginkgo. It also suggests that the cupules of corystosperms may be less distinct from those of Caytonia than has previously been supposed.
authors: State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing, 210008, China.|School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT, 06511, USA.
authors: Gongle
authors: G
authors: Shi
authors: Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, 02912, USA.
authors: Andrew B
authors: AB
authors: Leslie
authors: Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, IL, 60022, USA.
authors: Patrick S
authors: PS
authors: Herendeen
authors: Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, IL, 60022, USA.
authors: Fabiany
authors: F
authors: Herrera
authors: Paleontological Center, Mongolian Academy of Sciences, PO Box 260, Ulaanbaatar-51, Mongolia.
authors: Niiden
authors: N
authors: Ichinnorov
authors: Department of Environmental Sciences, Faculty of Sciences, Niigata University, 8050, 2-cho, Ikarashi, Nishi-ku, Niigata, 950-2181, Japan.
authors: Masamichi
authors: M
authors: Takahashi
authors: Botanischer Garten Rombergpark, Am Rombergpark 49b, Dortmund, 44225, Germany.
authors: Patrick
authors: P
authors: Knopf
authors: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT, 06511, USA.
authors: Peter R
authors: PR
authors: Crane
mesh_terms: D029624:Ferns / Q000033:anatomy & histology*; D005580:Fossils / Q000033:anatomy & histology*; D008986:Mongolia; D056771:Ovule / Q000033:anatomy & histology; D018515:Plant Leaves / Q000033:anatomy & histology; D012639:Seeds / Q000033:anatomy & histology
keywords: Early Cretaceous; Mongolia; corystosperms; homology; seed; seed ferns