关于新疆准噶尔盆地中侏罗世奥勃鲁契夫银杏(Ginkgo obrutschewii Seward)叶表皮构造的讨论

Discussion on leaf cuticular characters of Ginkgo obrutschewii Seward from Middle Jurassic of Junggar Basin,Xinjiang,China

通过对新疆准噶尔盆地白杨河地区中侏罗世奥勃鲁契夫银杏(Ginkgo obrutschewii Seward)模式产地及其邻区该种叶化石表皮构造的研究,笔者认为应以采自白杨河模式产地的化石材料作为认定该种主要特征的依据。尽管G.obrutschewii的外部形态和叶表皮构造可能具有一些变异特征,但综合而言,该种叶表皮构造主要特征似应为:表皮气孔器特征通常为下气孔式,上下表皮细胞均普遍发育强度不同的角质化丘状或低缓的乳状突起,垂周壁略直或微弯;气孔器单唇式,保卫细胞近孔缝处唇状加厚强烈,副卫细胞通常强烈角质化,表面常发育瘤状或团块状角质化加厚。目前对该种叶化石的采集及其表皮构造的研究尚不充分,相关研究有待进一步深入。近年来,俄罗斯学者归于本种的产于新疆福海的银杏叶片化石,及其对本种叶表皮构造特征的补充等,尚值得商榷。

Through the study of the leaf cuticles of Ginkgo obrutschewii Seward in the Middle Jurassic strata of Baiyanghe where the holotype fossil was yielded,and its neighboring areas in the Junggar Basin,Xinjiang,China,the author suggests that the specimens from the Baiyanghe,the holotype fossil locality,are the base for recognizing the leaf cuticular characters of the taxon. Despite of some variations in its leaf shape and cuticular characters,integrating all the available information,the general features of the leaf cuticular characters of this taxon have been recognized as follows： the cuticles basically hypostomatic,ordinary epidermal cells usually cutinized and bearing less prominent cuticular dome and gentle smaller papillae in periclinal walls,and the anticlinal walls usually straight or uneven less sinuous. Stomata haplocheilic,the guard cells usually cutinized in lip-form surrounding the stomatal aperture,and subsidiary cells usually cutinized with lumps. However,the collecting and studying work ofthe holotype and topetype fossils of this taxon are not enough,further study on the leaf cuticular features of Ginkgo obrutschewii is still needed. In addition,further discussions are needed on the rationality of the identification of this taxon from the Fuhai of northern Xinjiang reported by Nosova et al.（2011）.