REPRODUCTIVE BIOLOGY OF THE CERRO CUADRADO (JURASSIC) FOSSIL CONIFERS: PARARAUCARIA PATAGONICA

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Abstract
Seventy‐two silicified cone specimens of Pararaucaria patagonica Wieland from the Cerro Cuadrado (Jurassic) petrified forest in Patagonia were studied by use of thin sections and reflected light. Traces from the cone axis stele to the bract and ovuliferous scale are separate at their origins. In cross section the abaxially concave ovuliferous scale trace and massive circular bract trace branch half‐way out into the cone‐scale complex. Two triangular‐shaped bundles of fibers follow the scale trace into the laminar part of the ovuliferous scale. Both surfaces of the ovuliferous scale possess hairs which may have assisted in cone closure. Cones typically contain one flattened, winged seed per ovuliferous scale. Multi‐layered seed integuments are represented by an inner fleshy layer of large cells filled with a black amorphous material, a sclerotesta consisting of wedges or fan‐shaped groups of sclereids oriented at right angles to the seed surface, and a thin, often crushed fleshy layer. Seed wings consist of anastomosing, branched cells resembling glandular hairs and containing many intercellular spaces. Well‐preserved polycotyledonous embryos containing up to eight cotyledons are present in several cones. Tissues of the embryo including the shoot apex, calyptroperiblem, hypocotyl, and cotyledons are described. On the basis of anatomical and morphological features, specimens of P. patagonica are compared to members of both extant and extinct families of conifers including the Araucariaceae, Taxodiaceae, Pinaceae, Cupressaceae, and Cheirolepidaceae.
Funding Information
  • National Science Foundation (BMS 75–14221, BMS 74–21105)