RECONSTRUCTION OF THE JURASSIC CONIFER SEWARDIODENDRON LAXUM (TAXODIACEAE)

Compressed seed cones and pollen cones of Sewardiodendron laxum are de scribed from the Middle Jurassic of Yima, Henan, central China. They a re either organically attached to or associated with leafy shoots. See d cones are terminally borne. Each cone is ovate to elongated, up to 6 .5 cm long and 3.5 cm wide, and consists of a stout axis and numerous helically arranged bract-scale complexes. The bract protrudes beyond a nd is partially fused with the reduced ovuliferous scale. The ovulifer ous scale bears approximately six inverted, small, and flattened seeds . Pollen cones are borne in terminal clusters. Microsporophylls are he lically arranged, each bearing three abaxial, basally fused pollen sac s. Pollen is assaccate, rounded, and with an inconspicuous pore. Morph ological, structural, and cuticular features of seed cones, pollen con es, and leafy shoots of S. laxum are compared with those of fossil and extant conifers. S. laxum is included in Taxodiaceae and believed to have its closest affinities with a Mesozoic conifer Elatides and a gro up of Cunninghamia-like conifers. It is reconstructed as a half-evergr een tree that lived in a humid, warm-temperate climate.