辽宁昌图下白垩统沙河子组Elatocladus submanchurica Yabe et Oishi(亚东北枞型枝)的新发现

New discovery of Elatocladus submanchurica Yabe et Oishi from Lower Cretaceous Shahezi Formation of Changtu in Liaoning,China

松柏类亚东北枞型枝(Elatocladus submanchurica)和东北枞型枝(E. manchurica)在分类和使用上长期存在争议。笔者在辽宁昌图沙河子下白垩统沙河子组新发现的亚东北枞型枝的枝叶化石,其叶片总体呈条形、近扁平,具略凸显的中脉;叶表皮构造呈双面气孔式、气孔器孔缝不定向或多具斜向、保卫细胞及副卫细胞内侧强烈角质化。上述特征与Yabe&Oishi (1933)在吉林陶家屯附近下白垩统地层中建立的本种模式标本基本一致;与产自辽宁凤城碾子沟中侏罗统的东北枞型枝模式标本有较明显的区别。本次开展的角质层研究,首次补充了亚东北枞型枝的叶部表皮构造特征。基此,亚东北枞型枝(Elatocladus submanchurica)应作为独立的分类群继续在中生代植物分类系统中使用。

The classification and use of coniferous Elatocladus submanchurica and E.manchurica have been controversial for a long time.Some leafy shoot fossils of E.submanchurica from the Lower Cretaceous Shahezi Formation in Shahezi of Changtu,Liaoning,newly found by the authors,reveal the leaves featured by striped and nearly flat shape,with a midvein slightly clear on the leaf surface,and its cuticles amphistomatal in type and haplocheilic and disoriental(or mostly oblique in orientation)in stomata with strongly cutinized guard cells and subsidiary cells in their inner edges.All the characters are basically consistent to those of the type specimen of E.sub-manchurica from the Lower Cretaceous of Taojiatun in Jilin,and the present study has enriched the knowledge on this taxon in cuticular features for the first time.The type specimen of E.manchurica from the Middle Jurassic of Nianzigou of Liaoning,is clearly different from E.submanchurica in leaf features.Thus,E.submanchurica should be still regarded as an independent taxon,and remained to use in the Mesozoic plant classifications.