鄂西九里岗组植物化石新属种

NEW GENUS AND SPECIES OF FOSSIL PLANTS FROM JIULIGANG FORMATION IN W. HUBEI

报道了采自鄂西晚三叠世九里岗组的植物Radiatifolium magnusum gen. et sp. nov.,并订正了种名 Nilssonia hubeiensis nom. nov..因新属裂片的形态和脉序等与古生代的 Rhipidopsis 有些接近,认为其分类位置属银杏类的可能性较大;依据叶的分裂方式比较简单,裂片大小相差不大等,推测它可能代表银杏类中比较原始的类型.此外,对九里岗组植物群与我国南、北两个晚三叠世植物群的关系也作了扼要的讨论.

The fossil plants described in this paper were collected from the Jiuligang Formation in W. Hubei. They were in coexistence with the plants Danaeopsis fecunda Halle, Symopteris zeilleri (P'an) Hs, Lepidopteris ottonis (Goepp.) Schimper, Sinoctenis minor Feng, Drepanozamites cf. nilssoni (Nath.) Harris, Sphenozamites changi Sze, Glossophyllum shensiense Sze, etc., indicating that the plant-bearing bed belongs to Late Triassic in age. DESCRIPTION OF NEW GENUS AND SPECIES Radiatifolium gen. nov. Type species Radiatifolium magnusum gen. et sp. nov. Diagnosis Leaf very large, with a petiole. Segments stretching radiantly from top of petiole, roughly equal in size, cuneate, with broadly rounded apex. Veins radiate, dichotomizing, persisting to apex of segments. Reproductive organ unknown. In the general form and veins of segments, this new genus is very similar to Rhipidopsis Schmashausen, but in the latter, the leaf is flabellate the segments decrease orderly in size from the middle toward the outermost part of the leaf, with a lower gap. Description Late Triassic, Hubei, China. Radiatifolium magnusum gen. et sp. nov. (Pl. I, figs. 1, 2; Pl. II, figs. 1, 2) Leaf very large, composed of about 10-14 segments; petiole attaining a length of 7.8cm and a breadth of about 3mm. Segments cuneate, roughly equal in size, 10-11 cm long and 2-4 cm at the top, with obtusely rounded apex. Veins radiate, dichotomizing, fine and dense, numbering 35-40 per cm in the upper part of segments. Locality Donggong, Nanzhang County, Hubei. NUssonia hubeiensis nom. nov. (Pl. I, fig. 3; Pl. 3, figs. 3, 4) 1984 Nilssonia magnifolia Chen, p. 597, pl. 251, fig. l. Leaf very large, simply pinnate, more than 13 cm long; rachis about 4 mm wide. Segments attached to the upper surface of the rachis, covering most part of the rachis, belted, subopposite, more than 10.5 cm in length and 1.8-2.2 cm in breadth, conspicuously decurrent at the base. Veins differentiated into thick and interstitial ones, arising at an acute angle from the rachis, and then running almost parallel to the margins and persisting to the apex of the segments. Thick veins simple, numbering 8-12 in each segment; interstitial veins simple or bifurcating only once near the base, numbering 5-7 between two thick veins. Locality Hujiazui, Nanzhang County, Hubei.