摘要
Abstract;In this paper a new species of anatomically-preserved lepidodendralean stem is described from coal balls in the No.16 coal seam of the Taiyuan Formation in Shanjialin Coal Mine,Tao-Zao Coal Field,southern Shandong Province.The stem has a well preserved stele,outer cortex,periderm and leaf cushions preserved.Its organization is protostelic and it lacks secondary xylem.Outer cortex consists of alternatively arranged radial thick-walled cell bands and damaged thin-walled cell areas.Periderm is well developed,4-5 mm wide,and is divided into phellem and phelloderm.Phelloderm is wider than the phellem and is generally uniform but in some places is differentiated into alternatively arranged zones of tangentially thicker-and thinner-walled cell bands.Leaf cushions are approximately equidimensional orrhomboidal in tangential section,whereas leaf scars are slightly elevated and are probably lenticular orhelmet-like in shape,located at the upper part of the leaf cushion.Leaf cushions are flat and lack a welldeveloped keel or plications.Leaf traces extend through a horizontal course in the cushion and turnupwards slightly and then horizontally into the leaf scars,resulting in the outermost parts of the coursebeing somewhat"S"shaped.In radial section ligule pits are obliquely orientated with a broad basic part andits aperture is directly located at the top of the leaf scar.The ligule is large,ovoid in shape,andapproximately 1.2 mm long and 1.0 mm wide.Compared with the stems of other genera in Lepidodendrales,the stem under discussion is most comparable to the stems of Diaphorodendron to which it is hereassigned.Each of the three previously known species of Diaphorodendron occur in the middle LateCarboniferous of the Euramerican Flora and are distinct from the stem under discussion in the form of theleaf cushions.These differences support the erection of a new species,D.rhombicum,representing thefirst discovery of the genus from late Late Carboniferous and Permian ages worldwide,and also representingthe first occurrence of the genus within the Late Palaeozoic Cathaysian Flora.It is very interesting that the new species bears equidinensional leaf cushions with that probably represents a derived feature with inthe genus,while the leaf cushions with greater vertical than horizontal dimension occupied by the Euramerican species of Diaphorodendron are here considered ancestral in morphology.This hypothesis is supported by the younger geological age(late Late Carboniferous or early Early Permian)of the new species than that(middle Late Carboniferous)of the previously known Euramerican species of Diaphorodendron.
报道了产于山东枣庄矿区太原组16号煤层煤核(早二叠世早期或晚石炭世晚期)中一种具解剖构造的鳞木目茎。茎呈压扁状,长轴约6cm,短轴约2.5cm。中柱、外部皮层、周皮和叶座均保存。茎具原生中柱,无次生木质部发育,外部皮层由较发育的径向的厚壁的细胞条带和已经毁坏的薄壁的细胞区域交替排列构成。周皮较发育,厚约4~5mm,由木栓层和栓内层构成。其中栓内层较厚,细胞构造均一,或在有些地方分化为弦向的薄壁的细胞条带和厚壁的细胞条带,二者交替排列。其中薄壁的细胞条带常保存不好而形成弦向的裂隙。叶座的高和宽近相等,呈近正菱形。叶痕盔形或双凸镜形,位于叶座上部,微微突出于叶座表面之上。叶座表面平坦,未见明显的中脊和横皱纹。叶迹在叶座内近水平状延伸,但在近叶座表面处略向上然后向外弯曲成不太明显的“S”形进入叶痕内。径切面上叶舌穴略向上斜伸,具一宽大的基部,其开口直接位于叶痕顶角处。叶舌大,宽卵球形,长轴达1.2mm,短轴达1mm。与目前已知的鳞木目几个属的茎比较,当前标本与Diaphorodendron属的茎最为接近,仅在叶座上有些不同,本文将其归人该属内。Diaphorodendron属目前共有3个种,全分布于欧美植物区晚石炭世中期(威斯法期),它们与当前标本区别明显,因此,将当前标本归人新种D.rhombicum内。本文是国内首次报道Diaphorodendron属在华夏植物区的存在。其高和宽近相等的叶座形态可能表明了一种进化的特征,这从其所在地层的地质时代(早二叠世早期或晚石炭世晚期)较欧美植物区的3个种(晚石炭世中期)较新这一事实得到支持。
基金
中国科学院创新方向性项目(KSCX2-SW-108)
国家自然科学基金(39970056)
中国科学院植物研究所部署“前沿领域”项目。
