摘要
根据生殖器官类型,继将二叠枝脉蕨(cladophlebis permica Lee et Wang)的华南标本改归天石蕨属(Szea)之后,为该种的华北标本另建了-新的属名——李氏蕨属(Lixotheca),并再次表述了该种华南标本改归Szea的理由.根据对孢子囊群、孢子囊及孢子结构的研究,认为Lixotheca归入膜蕨科的理由是较为充分的.而Szea则应被归入里白科.
As a more comprehensive form genus, Cladophlebis is used mainly for the sterile fronds prevailed in the Mesozoic flora, though this group of plants made their first appearance in the Permian period as forerunners. It is well worth notice that up to date 20 species of the genus have been described in the Gigantopteris Flora in China, i.e., Cladophlebis nystroemii Halle, 1927; Cl.? yongwolensis (Kaw., 1927) Stockm. et Math., 1939; Cl. manchurica (Kaw., 1927) Gu et Zhi, 1974; Cl. ozakii Yabe et Oishi, 1938; Cl. permica Lee et Wang, 1956; Cl. connexa J. H. Zhang, 1978; Cl. alata Yang et Chen, 1979; Cl. (Oligocarpia?) crenata Yang et Chen, 1979; Cl. rhomboidea-ovata Yang et Chen, 1979; Cl. henanensis Zhang et Mo, 1979; Cl. fuyuanensis Zhang, 1980; Cl. parapermica Zhang, 1980; Cl. yunnanica Zhang, 1980; Cl. paraozakii Li, Yao et Deng 1982; Cl. fissilis Zhu, Hu et Z. J. Li, 1984; Cl. liulinensis Xiao, 1985; Cl. deltata Yang, 1987; Szea (Cladophlebis) sinensis Yao et Taylor, 1988; Cladophlubis? lanceolata Si, 1989 and Chansitheca (Cladophlebis) anxiensis S. S. Li, 1989.
shaped, sheathing the basal part of the elongated receptacle. Sporangia numerous in each sorus, most probably rounded, arranged quincuncially; annulus complete, oblique or transverse.
Type-species Lixotheca (Cladophlebis) permica (Lee et Wang) comb. nov.
Etymology 'Lix', abbreviated from Li Xing-xue, and 'theca', Greek, in honor of Prof. Li Xing-xue, who first described the sterile frond of the type species with Mr. Wang Shui.
Occurrence Permian; China.
Lixotheca (Cladophlebis) permica (Lee et Wang) comb. nov. (Pl. Ⅰ-Ⅲ; Text-figs. 1,2)
Sterile frond large, at least bipinnate. Shape of penultimate pinnae (Pl. I, fig. 2) unknown, with preserved part measuring about 18cm in breadth and 11cm in length. Pinna rachis 2.5-3.5mm broad, finely striated. Ultimate pinnae linear, with acuminate apices, alternate, forming an angle of 50°-70° with the rachis, crowded, at least 11cm long and about 2cm broad in the middle part; ultimate rachis only 1mm in breadth, finely striated. Pinnules crowded, attached with the entire base, oblong-deltoid, slightly falcate and provided with obtuse to acute apices, normally often 12-16mm long and 6-8mm broad at base; margin entire to serrate. Midvein rather thin, but distinct, deriving from the rachis at an angle of 40°-50°, decurrent, dissolving before reaching the apex. Lateral veins rather fine, bifurcating soon after departing from the midvein at very acute angles, with anterior branch dividing 1-2 times, and posterior branch undividing or dividing once more; veinlets of a lateral vein corresponding to a tooth or lobe of pinnule margin. Catadromic basal pinnule of the ultimate pinna larger, bearing 1-2 lobes and slightly touching or decurrent on the penultimate rachis, while anadromic basal pinnule parallel to penultimate rachis.
Fertile frond homogeneous with sterile frond. Specimen shown in pl. I, fig. 1 at least bipinnate, with half-breadth attaining 12.5cm. Penultimate rachis 3-3.5cm in breadth, with 3 fine longitudinal grooves on ventral impression (Pl. Ⅱ, fig. 3), and 2 fine ribs on dorsal impression (Pl. Ⅱ, fig. 1); rounded dots of 0.03mm in diameter scattered on rachis (Pl. Ⅱ, figs. 1,3). Ultimate pinna attaining 13cm in length, with a breadth of 2cm in middle part, forming an angle of 60° with penultimate rachis, alternate, linear, with acuminate apex. Ultimate rachis only 1mm broad, with 2 longitudinal striae, and rounded dots of 0.03mm in diameter scattered on surface (Pl. Ⅱ, fig. 2). Pinnules relatively large, crowded, attached to the rachis with the entire base, about 1016mm long, and 6mm broad in basal part, oblong-deltoid, falcate, provided with acute to obtuse apices; margin entire to serrate (Pl.,Ⅱ, figs. 4,5; text-fig. 1). Venation of open type. Midvein distinct, forming an angle of 30°-40° with the rachis, slightly decurrent, dissolving before reaching the apex. Lateral veins rather thin, forming an acute angle with the mid-vein, and then slight- ly bending forward and bifurcating at sharp angles, with anterior branch often dividing once or twice more, and posterior branch undividing or sometimes dividing once more; lowest pair of lateral veins generally forking more times than the others. Veinlets bearing sori at the end becoming more distinct and thicker than ordinary veins. Catadromic basal pinnule of ultimate pinna larger, bearing 1-2 lobes and slightly touching or decurrent on the penultimate pinna rachis (Pl. Ⅱ, figs. 1, 3; text-fig. 2). Midvein of the lobed catadromic basal pinnules rather thick, forking immediately into two branches after arising from the rachis; anterior branch entering into the main lobe, often forking 3 times, while posterior branch usually forking twice, and sometimes forking into 2 equal branches and entering into corresponding smaller lobes.
Sori oblong to cylindric, slightly pendent, 3.2-(4.0)-5.2mm long and 1.2-(1.5)1.9mm broad, marginal in origin, sitting at the ends of veins, usually numbering 5-7 in a pinnule. Indusium obviously cup-shaped, surrounding base of
出处
《古生物学报》
CAS
CSCD
北大核心
1993年第5期525-539,653-656,共15页
Acta Palaeontologica Sinica
基金
国家自然科学基金
