吉林延边地区下白垩统长财组铁角蕨属一新种

A New Species of Asplenium L. from the Lower Cretaceous Changcai Formation in Yanbian Area,Jilin,China

现生铁角蕨Asplenium Linn.种类繁多,广布于热带-温带地区,以热带-亚热带为分布中心。确切的Asplenium Linn.化石最早出现于东亚和俄罗斯远东地区的下白垩统地层中,是西伯利亚-加拿大区白垩纪的新生分子。根据吉林延边地区下白垩统长财组发现的铁角蕨化石的营养羽片和生殖羽片标本,在原位孢子研究基础上,通过与现生铁角蕨植物繁殖器官的对比,确认当前材料属于Asplenium Linn.;并进一步与国内外相关属种进行比对,建立了一个新种---长财铁角蕨(新种)(Asplenium changcaium Sun etLiu,sp. nov.)。该新种原位孢子的研究为深入探讨铁角蕨属乃至铁角蕨科的系统演化奠定了基础。

The living family of Aspleniaceae might be one of the biggest families of ferns. The Genus among it is diversified and widely distributed in tropical-temperate zones, especially in the tropical and subtropical areas which is recognized as the distribution center. Confessed earliest fossil specimens of Asplenium Linn. were found from Lower Cretaceous of Northeast Asia and Far East of Russia, being one of the new elements in Cretaceous in the - fertile Siberian-Canadian Phyto-geographic Realm. Based on the comparative studies of in situ spores between the frond fossils collected from the early Cretaceous Changcai Formation in Yanbian area of Jilin, China, and the living fertile fronds of Asplenium trichomanes L. , the fertile frond fossils and its sterile frond fossils are definitely assigned to the genus Asplenium L. Furthermore, through the comparison to the known species of fossil Asplenium, a new species of Asplenium is recongnized, i. e. Asplenium changcaium Sun et Liu, sp. nov. Since the well preserved spores in situ of the present new species, it would be beneficial for the researches on the evolution of Asplenium, or even Aspleniaceae. The new species is described as follows： Order ： Filicales ; Family ： Aspleniacea ; Genus ： Asplenium Linn. , 1753 ; Species ： Asplenium changcaium Sun et Liu, sp. nov. （Fig. 2-1 - 8, Fig. 3-1 - 7） Holotype： The specimen JLC030344 illustrated on Fig. 2-1 has been chosen as holotype. Paratype： Both the specimen JLC030359 illustrated on Fig. 2-5 and the specimen JLC030447 illustrated on Fig. 2-7 are chosen as paratypes. Additional specimen： JLC030343, JLC030345, JLC030346, JLC030348, JLC030442, JLC030358, JLC030356, JLC030443, JLC030353. Repository： the Research Center of Paleontology and Stratigraphy, Jilin University, China. Type locality： Nanyang Coal-mine, Helong County, Jilin Province. Type horizon： Changcai Formation, Lower Cretaceous （Aptian）. Etymology： Changcai refers to the stratigraphic horizon, the Lower Cretaceous C.hangcai Formation in Yanbian area, Jilin Province. Description ： Frond, bi- or tri-pinnate, length unknown, portions preserved maximum 10 cm long. Main rachis 1.0 - 2.5 mm wide, abaxial surface round, convex and with mid-rib ; adaxial surface flat, concave and with midgroove ; rachis flanges forming by decurrence of pinna rachis. Pinna rachis, having same structure as main rachis, but quite slender, 0. 15 -0. 50 mm wide. Sterile pinnae, broad lanceolate, 41 ～ 51 mm long and 29 -37 mm wide, about 15 -25 mm apart, attachment sub-opposite or alternate at angle of about 70 on raehis. Pinnules, lanceolate, length 10 - 25 mm long and 5 - 7 mm wide, about 5 mm apart, anadromic, attachment opposite or alternate at fight angle on rachis, tapering gradu- ally arrow tailed, apex obtuse. Pinnule base, decurrent obviously on rachis with a short handle, about 0.5 mm long. Margins, dissected into 5 - 7 pairs of segments. The segments on acroscopic side of pinnule, oval, 3 ～ 4 mm long and 2 -3 mm wide, apex obtuse, attachment at angle of about 80 on mid-vein, margins entire, indented or slightly re-dissected into 3 lobs, particularly in basal segments. Those on basiscopic side of pinnule, lanceolate, length 3 ～ 4 mm, width 1 ～ 1.5 mm, margins entire, apex obtuse, attachment at angle of 30 - 45 on mid-vein. Veins, distinct, lateral veins, anadromic, diverge 2 - 3 times and reach margin, convex, 3 ～ 5 veins along segment margins, usually dilatant at the end of every small vein. Lamina thin. Fertile pinnae, occupying the upper part of pinnae, bi-pinnae or tripinnae, slightly narrower than sterile pinnae. Fertile pinnules, laneeolate, 7 -20 mm long and 3 -7 mm wide, having a short decurrent handle too. Soft,elliptical,0. 7 mm long and 0. 4 mm wide, situated on every segments of pinnules, attachment longitudinally at the middle part of vein, with elliptical cup （0.30 mm long and 0. 18 mm wide） on acroscopic side of sorus. Sporangia, elliptoidal, 100 μm long and 72μm wide, with erect annulus composed of 15 or 16 cutinized cells, 18 - 19μm from interior to exterior. Miospores, fabaceous, polar axis 18 - 20 μm wide, equatorial axis 30 ～ 35μm long, monolete 10 ～12 μm long, walls smooth, thickness about 1.7 μm, perine unknown. Discussion： Specimens identified as Asplenium changcaium Sun et Liu, sp. nov. include 8 sterile leaves JLC030343-030348, 030358, 030442） and 4 fertile leaves （JLC030359, 030353,030356, 030443）. Specimen shown in Fig. 2-6 might be the lower part of leaf for the reason that the ultimate pinnae and pinnulae are slightly smaller than the normal ones, and the main rachis is much thicker than that shown in Fig. 2-5. Specimen shown in Fig. 2-7 connects the sterile leaves with fertile fronds. The fertile basal pinnulae on acroscopic side of pinna are still oval in shape and slightly bigger than the others. This is quite similar to the sterile ones. Comparison： The spores in situ of Asplenium changcaium Sun et Liu, sp. nov. shown in Fig. 3-1 -7 are quite similar to the living Asplenium trichomanes L. shown in Fig. 3-8 -10, in the shape of spores, sporangia and annulus, and also similar in the size of spores. It is reasonable to assign the fossil materials to the living genus Asplenium L. The sporangia of the living Asplenium trichomanes L. is 200 - 220μm long and 160 - 170 μm wide, almost two times of the size of sporangia of Asplenium changcaium Sun et Liu, sp. nov. The number of cutinized cells on annulus and the size of spores are the same on both the present fossil species and the living species. Clearly, the number of spores containing in the sporangia of living Asplenium trichomanes L. is bigger than that of the Early Cretaceous Asplenium changcaium Sun et Liu, sp. nov. This tells us that one of the main evolutionary routs of Asplenium L. might be the enlargement of sporangia and the enhancement of reproductive ability. Living Asplenium exceeds 660 species, distributed worldwide, especially in the tropical and subtropical regions （Wu Shiewhong, 1999）. Fossil species assigned to Asplenium are less than 10. Asplenium tiefanum Deng from the Lower Cretaceous Xiaoming＇anbei Formation of Tiefa basin, Liaoning, China is similar to the present new species to some extent. However, the Aspenium tiefanum Deng never have the specialized oval segments on acroscopic side of pinnule and 2 - 3 times forking lateral veins ; and the sori （ length 1-2 mm, width 0.6 -0.8 mm） and sporangia （ 150 μm in diameter） are much bigger than, almost two times of that of Asplenium chartgcaium Sun et Liu sp. nov. Having much smaller ultimate pinnae and pinnules, Asplenium parvum Ren from the Lower Cretaceous Yimin Formation of Hailar basin, Inner Mongolia, China is different from the new species. And the sori of A. parvum Ren, situated in the inter-venular areas are usually 1 -2 mm long, much longer than those of A. changeaium Sun et Liu, sp. nov. , which situated directly on the lateral veins. As for the Asplenium popovii Samylina and Asplenium samylinae Krassilov, their pinnules are Cladophlebis- type, and their sori are long elliptical or crescent, which is distinctly different from the Asplenium changcaium Sun et Liu, sp. nov. The other materials assigned to Asplenium, such as Asplenium dicksonianum Heer, Asplenium rigidum Vassil- evskaya, there are not any fertile organs of this two species found. The sterile pinnae, pinnules and veination of A. dicksonianum and A. rigidum are Sphenopteris-type, attachment at a narrow angle on rachis, which is quite different from those of A. changcaium Sun et Liu, sp. nov.