ANATOMICALLY PRESERVED VOJNOVSKYALEAN SEED PLANTS IN UPPER PENNSYLVANIAN (STEPHANIAN) MARINE SHALES OF NORTH-AMERICA

Upper Pennsylvanian dysoxic marine shales of midcontinent North Americ a yield permineralized remains of apparently extrabasinal vegetation. A large percentage of the plants are surprisingly unlike the well know n swamp, fluvial and lacustrian floras of the late Paleozoic paleotrop ics, revealing numerous aspects of the morphology, anatomy and reprodu ctive biology of plants that may have been ancestral to the dominant t axa of the Mesozoic. Included among the assemblages are ovulate conife rophyte remains that demonstrate the occurrence of vojnovskyalean seed plants in equatorial Euramerica. Specimens consist of simple ovulate cones that are more-or-less clustered along eustelic stems in the axil s of helically arranged, strap-shaped leaf bases, and are described as Sergeia neuburgii new genus and species. Individual cones are up to a pproximately 2 cm long and 1.5 cm in maximum diameter, with helically arranged scales and sporophylls that diverge from a eustelic axis. Sca les occur in the basal region of the cone, and are laminar and pointed . Sporophylls are borne distally. One specimen shows about 45 sporophy lls, each of which terminates as one erect ovule. Most of the other co nes have abraded apices, and terminate in relatively terete foliar app endages that are interpreted to be sporophyll bases. Ovules are flatte ned and winged, approaching 180 degrees rotational symmetry. Integumen t histology, vascular tissue distribution and pollen chamber structure are similar to those of cordaiteans and callistophytalean seed ferns. Sergeia adds to the number of late Paleozoic conifer-like plants that do not conform to the Pinopsida as traditionally circumscribed, and p oses additional questions to assumptions of monophyly for coniferophyt es and for conifers sensu lato.