Reconstruction of the Pennsylvanian-age walchian conifer Emporia cryptica sp. nov . (Emporiaceae: Voltziales)

Abstract

This paper provides a whole plant concept for a new species, Emporia cryptica sp. nov. Hernandez-Castillo, Stockey, Rothwell & Mapes (Emporiaceae: Voltziales), the fourth conifer to be reconstructed from the rich fossil biota at the Late Pennsylvanian, Hamilton Quarry, Kansas. E. cryptica has an orthotropic stem, lateral plagiotropic branches with simple leaves, simple pollen cones, and compound ovulate cones. Branches have an endarch eustele with dense wood surrounding a parenchymatous pith with sclerotic nests/plates, and secondary xylem tracheids with multiseriate hexagonal bordered pits. Leaves on both penultimate and ultimate branches are simple and amphistomatic with two adaxial stomatal bands, monocyclic and dicyclic stomata, and two narrow abaxial rows of stomata with numerous trichome bases. Pollen cones are simple with helically arranged microsporophylls and adaxial pollen sacs. Prepollen is monolete, eusaccate, and monosaccate ( Potonieisporites Bharadwaj). Ovulate cones are compound with bilaterally symmetrical dwarf shoots in the axils of helically arranged forked bracts. Axillary dwarf shoots bear numerous sterile scales interspersed with two megasporophylls, each bearing a single inverted terminal ovule. This plant displays morphological and cuticular characters similar to several morphogenera of Paleozoic walchian conifers but is most comparable to the fossil plant species Emporia lockardii and Hanskerpia hamiltonensis. E. cryptica is the only walchian conifer where ovules and seeds with megagametophytes, immature embryos and mature embryos have been documented, demonstrating that the most ancient conifers possessed seed dormancy and polycotyledonary embryos. This reproductive biology is similar to that of many Mesozoic and extant conifers with saccate pollen except for the presence of prepollen grains that are common among Paleozoic walchian conifers.