Department of Biological Sciences, LSCB 124, University of South Alabama, Mobile, Alabama 36688 USA;
Am J Bot. 2000 Jun;87(6):757-68.
A new Triassic corystosperm is described from the Shackleton Glacier region of Antarctica. The compression fossils include cupulate organs (Umkomasia uniramia) and leaves (Dicroidium odontopteroides) attached to short shoot-bearing branches. The cupulate organs occur in groups near the apices of the short shoots, and each consists of a single axis with a pair of bracts and a subapical whorl of five to eight ovoid cupules. This unique architecture indicates that the cupules are individual megasporophylls rather than leaflets of a compound megasporophyll. A branch bearing an attached D. odontopteroides leaf provides the first unequivocal evidence that Umkomasia cupulate organs and Dicroidium leaves were produced by the same plants. Although this had previously been assumed based on organ associations, the new specimens are important in demonstrating that a single species of corystosperm produced the unique cupulate organs described here and the geographically and stratigraphically widespread and common D. odontopteroides leaf. Therefore, biostratigraphic, paleoecological, and phylogenetic studies that treat Dicroidium leaf morphospecies as proxies for biological species of entire plants should be reconsidered. Phylogenetic analysis suggests that the corystosperm cupule is an unlikely homologue for the angiosperm carpel or outer integument.
一种新的三叠纪科雷斯特斯珀姆植物来自南极洲沙克尔顿冰川地区。压缩化石包括杯状器官（Umkomasia uniramia）和叶子（Dicroidium odontopteroides），附着在短枝上。杯状器官成群地出现在短枝的顶端附近，每个器官由一个单一的轴组成，轴上有一对苞片和一个亚顶的五到八个卵形杯状结构。这种独特的结构表明，杯状结构是单个大孢子叶，而不是复叶大孢子叶的小叶。一个带有附着的 D. odontopteroides 叶子的分支提供了第一个明确的证据，证明 Umkomasia 杯状器官和 Dicroidium 叶子是由同一植物产生的。尽管这以前是基于器官组合假设的，但新标本在证明一种科雷斯特斯珀姆植物产生了这里描述的独特杯状器官以及在地理上和地层上广泛分布且常见的 D. odontopteroides 叶子方面非常重要。因此，将 Dicroidium 叶子形态种作为整个植物的生物种的代理进行生物地层学、古生态学和系统发育研究应该重新考虑。系统发育分析表明，科雷斯特斯珀姆杯状结构不太可能是被子植物心皮或外种皮的同源物。
