Department of Biology, University of San Francisco, San Francisco, California 94117;
Am J Bot. 1998 Sep;85(9):1289-300.
Compressed seed cones and pollen cones of Sewardiodendron laxum are described from the Middle Jurassic of Yima, Henan, central China. They are either organically attached to or associated with leafy shoots. Seed 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 and is partially fused with the reduced ovuliferous scale. The ovuliferous scale bears approximately six inverted, small, and flattened seeds. Pollen cones are borne in terminal clusters. Microsporophylls are helically arranged, each bearing three abaxial, basally fused pollen sacs. Pollen is assaccate, rounded, and with an inconspicuous pore. Morphological, structural, and cuticular features of seed cones, pollen cones, 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 group of Cunninghamia-like conifers. It is reconstructed as a half-evergreen tree that lived in a humid, warm-temperate climate.
中华裂齿龙的压缩种子球果和花粉球果产自中国中部河南义马的中侏罗世。它们要么与带叶嫩枝有机相连，要么与之伴生。种子球果顶生。每个球果呈卵形至长形，长可达 6.5 厘米，宽 3.5 厘米，由粗壮的轴和许多螺旋状排列的苞片-鳞片状复合体组成。苞片突出并与退化的胚珠鳞部分融合。胚珠鳞带有大约六个倒生的、小而扁平的种子。花粉球果在顶生的簇中产生。小孢子叶螺旋状排列，每个小孢子叶带有三个背腹面、基部合生的花粉囊。花粉为囊状，圆形，有一个不明显的孔。中华裂齿龙的种子球果、花粉球果和带叶嫩枝的形态、结构和表皮特征与化石和现存针叶树进行了比较。中华裂齿龙被归入柏科，并被认为与中生代针叶树 Elatides 和一组类似杉木的针叶树关系最为密切。它被重建为一种半常绿乔木，生活在潮湿、温暖的气候中。
