RECONSTRUCTION OF THE JURASSIC CONIFER SEWARDIODENDRON LAXUM (TAXODIACEAE)

Citation
Xl. Yao et al., RECONSTRUCTION OF THE JURASSIC CONIFER SEWARDIODENDRON LAXUM (TAXODIACEAE), American journal of botany, 85(9), 1998, pp. 1289-1300
Citations number
51
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
0002-9122
Volume
85
Issue
9
Year of publication
1998
Pages
1289 - 1300
Database
ISI
SICI code
0002-9122(1998)85:9<1289:ROTJCS>2.0.ZU;2-W
Abstract
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.