Department of Ecology and Evolutionary Biology and Natural History Museum and Biodiversity Research Center, University of Kansas, Lawrence, Kansas 66045-7534 USA.
Am J Bot. 2002 Apr;89(4):664-76. doi: 10.3732/ajb.89.4.664.
The permineralized, corystosperm, cupulate, ovule-bearing organ Umkomasia resinosa is described from the early Middle Triassic of Antarctica. This is the first description of anatomically preserved Umkomasia, which consists of a determinate cupulate branch with helically arranged, recurved, pedicellate megasporophylls, each of which bears one or two abaxially attached unitegmic ovules. Cupules are ovoid, bilobed with elongate ventral and dorsal openings or unlobed with a single ventral opening, and have a two-zoned parenchymatous cortex and abundant secretory cavities. Ovules are small, orthotropous, and possess a thin integument that contains numerous secretory cavities. The ovules are broadly attached at the base, with a bifid integumentary apex that extends past the cupule lobes. The cupulate branch displays stem-like anatomy, producing paired traces into each cupule stalk. These structurally preserved ovulate organs can be related to other corystosperm organs from Antarctica, particularly the pollen-organ Pteruchus fremouwensis. Both anatomical and morphological features support interpretation of corystosperm reproductive structures as branching systems rather than as compound sporophylls. As a result of an increased understanding of the organization of Umkomasia, it appears doubtful that any direct relationship exists between the corystosperm and angiosperm lineages.
本文描述了产自南极洲早三叠世的矿化、拟杯柏型、杯状、具胚珠的器官 Umkomasia resinosa。这是首次对解剖学上保存的 Umkomasia 的描述，它由一个确定的杯状分枝组成，具螺旋状排列、弯曲、具花梗的大孢子叶，每个大孢子叶上着生一到两个背面着生、具单珠孔的合生胚珠。杯状结构为长椭圆形，具二裂或不裂的具长中肋的背腹侧开口，具有两区域的薄壁组织皮质和丰富的分泌腔。胚珠小，直生，具薄的珠被，含有许多分泌腔。胚珠基部广泛着生，具二分的珠被顶端，超过杯状结构裂片。杯状分枝显示茎状解剖结构，在每个杯状结构花梗中产生成对的痕迹。这些结构保存的具胚珠器官可以与南极洲的其他拟杯柏型器官相关，特别是花粉器官 Pteruchus fremouwensis。解剖学和形态学特征都支持将拟杯柏型生殖结构解释为分枝系统，而不是复合孢子叶。由于对 Umkomasia 组织的认识增加，看来拟杯柏型和被子植物类群之间似乎没有直接关系。
