鄂西晚泥盆世种子状结构武汉仙籽(Sphinxiocarpon wuhanium)的形态学研究  

MORPHOLOGICAL OBSERVATIONS OF THE SEED-LIKE STRUCTURE SPHINXIOCARPON WUHANIUM FROM THE UPPER DEVONIAN OF HUBEI,CHINA

作　　者：薛进庄[1] 

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871

出　　处：《古生物学报》2010年第4期461-471,共11页Acta Palaeontologica Sinica

基　　金：国家自然科学基金项目(Nos.40830211;40802003)资助

摘　　要：基于采自湖北长阳晚泥盆世黄家磴组(弗拉斯期)的新材料,对种子状结构武汉仙籽Sphinxiocarpon wuhanium(Li,Hilton and Hemsley)Wang,Xue and Prestianni进行比较形态学研究和几何形态统计分析。与模式产地(武汉米粮山珞珈群)的标本相比,长阳的标本显示出离体保存的单个种子状结构个体较大,具柄,囊状包被结构顶端收缩愈合,表面具纵向条纹,从柄延伸至顶端,而个体较小的种子状结构则聚成孢子叶球状。因此,仙籽属Sphinxiocarpon的个体发育早期阶段是一种孢子叶球状生殖形态,而发育后期通常脱落保存为单个的种子状结构,其母体植物可能是一种石松植物,但它与泥盆-石炭纪已知的异孢型石松类植物和前裸子植物都有较大差异,是一个很独特的分支。这些结果表明,在泥盆纪的前裸子植物-裸子植物谱系之外,同期其他植物类群(如石松植物)也演化出了与种子相似、具单一功能大孢子和包被结构的生殖器官,显示植物的生殖器官在不同类群中的趋同演化现象,它们可能以相似的方式(如减少大孢子数目、形成包被大孢子囊的结构等)来响应当时的环境胁迫。Based on new material collected from the Upper Devonian Huangjiadeng Formation （Frasnian） of Changyang,Hubei,China,morphological features of the seed-like structure Sphinxiocarpon wuhanium （Li,Hilton and Hemsley） Wang,Xue and Prestianni are reinvestigated. Compared to the specimens from the type locality （Luojia Group of Miliangshan,Wuhan）,the specimens from the Changyang locality,preserved as isolated seed-like structures,are larger in size. The whole seed-like structure is stalked,and the enclosing sterile envelop,with a tapering distal end,has longitudinal striations extending from the stalk to the distal end. Smaller seed-like structures are aggregated to form a strobilus-like organ. Thus,when in early phase of development （immature）,Sphinxiocarpon exhibits a strobilus-like fertile organ,while when in later phase （mature）,seed-like structures are always shed from the parent plants and then isolatedly preserved in the deposits. Sphinxiocarpon probably have a lycopsid affinity; however,it may represent a unique clade in light of the large discrepancies compared with the known heterosporous lycopsids. Besides the progymnosperm-gymnosperm lineages,fertile organs with one single functional megaspore and a sterile enclosing structure,comparable to ovules or seeds to some extent,have evolved in other groups by the Late Devonian. This is a typical phenomenon of convergent evolution,that is,plants from different lineages might have chosen a similar way,e.g.,in reduction of megaspore numbers and refinement of the enclosing structures of the sporangia in this case,to adapt to their local environments.

关 键 词：种子状结构 几何形态统计分析 趋同演化 石松纲 晚泥盆世 

分 类 号：Q915[天文地球—古生物学与地层学]