辽宁北票下白垩统义县组的单子叶被子植物新属种

TWO NEW TAXA OF MONOCOTYLEDONOUS ANGIOSPERM FROM LOWER CRETACEOUS YIXIAN FORMATION OF BEIPIAO,LIAONING

文章报道可能属于单子叶被子植物化石的两个新属Shangyuania gen.nov.和Zhouia gen.nov.,标本采自辽宁省北票市上园乡黄半吉沟下白垩统义县组尖山沟层。前者属于水生草本植物,具有一个非常细弱的茎,茎保存不全,未见分枝,茎上生有对生和互生的沉水型叶;叶线形,全缘,基部无柄,顶端为钝圆形;具有一条中脉,中脉的两侧各有3—4条细而平行的侧脉和在叶的远轴面上各有一行可能的通气组织;穗状花序生于叶腋中,具有一个细弱的花序梗,由4—5轮小花组成。后者是一个单独保存的种子,卵圆形,被压扁,表面具有多角形的细胞或泡沫状纹饰。通过对两新属形态特征研究和对比,推测它们可能与现生眼子菜科(Potamogetonaceae),特别是该科中的眼子菜属(Potamogeton),以及茨藻科(Najadaceae)的茨藻属(Najas)有某种亲缘关系。

Two new genera and species of monocotyledonuos angiosperm, Shangyuania caii gen. et sp. nov. and Zhouia beipiaoensis gen. et sp. nov. are reported here. The specimens were collected from Early Cretaceous Jianshangou bed of Yixian Formation in Huangbanjiegou village, Shanyuan town, Beipiao City, Liaoning Province. Shangyuania caii is considered as an aquatic herb. It has a very slim and fragile stem, and a rhizome and some root-like parts are preserved near by, likely belong to same plant, although they are not atta ched. Stem has no branching. I.inear leaves are likely submerged. They are alternately and oppositely arranged on the stem. Each leaf has a distinct midrib, in both sides of which ：3--4 parallel lateral veins are observed. On the lower side of some leaves two black lines can be seen, which are interpreted as aerating tissues. Leaves are sessile, entire, with apex obtusely rounded. Axillary spike has a gracile peduncle, consisting of 4 5 whirls of flowerets. Zhouia beipiaoensis is a separately pre served seed, ovate, flattened. Testa of seed is likely consisting of three layers： the cells of surface layer are rectangular, square or irregularly tetragonal in shape; middle layer cells are seen in cross-section, which appear to be isodiametric po lygonal cells; cells of inner layer are thin-walled, extremely fragile and very rarely preserved. Both plants are inferred to have a certain relationship with living Potamogetonaceae and Najadaceae of the monocotyledonous angiosperm, through careful investigation and comparison from their morphological features.