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保存有解剖构造和系统学信息的紫萁根茎化石对于探究地史时期紫萁科植物多样性特征以及起源演化具有不可替代的重要意义.我国冀北辽西地区是北半球为数不多的侏罗纪紫萁根茎化石产地之一,但目前我们对其化石多样性的了解还处于积累阶段.本文报道辽西地区新近发现的解剖特征保存完好的紫萁科矿化根茎化石新类型——王氏阿氏茎Ashicaulis wangii sp.nov.化石采自北票市长皋地区中侏罗统髫髻山组.标本呈近圆柱状,由髓、木质部圆筒、皮层及叶柄基外套组成.髓部异质,木质部圆筒由约15~17个木质部束组成,外韧网管中柱,具明显完整叶隙(即时型或延迟型);皮层分内、外两部分,含叶迹数目相对较少.该种具有异质叶柄基硬化环且叶柄基内部皮层含大量厚壁组织.在目前已知紫萁科Ashicaulis属具异质硬化环的5个种中,有4个种报道于中国,而南半球材料多以同质硬化环为典型特征,因而中国材料具有一定的地域性特征.新材料的发现不仅丰富了我国紫萁科根茎化石的属种类型,而且由于其在解剖特征上与产自北美古新统的Osmunda pluma Miller存在较高的相似性,对探究紫萁科植物的多样性特征、起源与辐射演化,以及该科在北半球的古生物地理学意义和宏演化过程提供了新的化石证据.
There are anatomical and systematic information preserved aster fossil rhizome fossils for exploring the gentian history, the diversity of plant characters and the origin of evolution has irreplaceable significance.Our country in western Liaoning Province is the western hemisphere, one of the few jurassic purple萁 rhizomatous fossils.However, our understanding of its fossil diversity is still in the accumulation stage.This paper reports the newly discovered anatomical features of western Liaoning Province, Ashicaulis wangii sp.nov. The fossils were collected from the Jurassic Chijixi Mountain Formation in the Changgao area, Beipiao City. The specimens were nearly cylindrical and consisted of a pulp, xylem cylinder, cortex and petiole base coat. The tube is composed of about 15 to 17 xylem bundles, and the outer column of the outer ductile tube has a clear complete lamella (immediate or delayed type). The inner and outer cortices have relatively few leaf tracts, Quality petiole-based hardened ring and the petiole-based inner cortex contains a large number of thick-walled tissues.At present, of the 5 species of Ashicales that belong to the genus Ashicaulis, 4 species are reported in China, quality Therefore, the discovery of new materials not only enriches the genus of rhizome fossils in China, but also because of its anatomical characteristics and the origin of North American Paleocene Osmunda pluma Miller has high similarity and provides new fossil evidence for exploring the diversity characteristics, origin and radiation evolution of the plants of the genus Prorocentrum as well as the Palaeogeography significance and macro-evolution of the family in the northern hemisphere.