A new species of Lepidostrobus from the Upper Devonian of Xinjiang, China and its bearing on the phylogenetic significance of the order Isoëtales

Lepidostrobus xinjiangensis sp. nov. is described from Upper Devonian rocks of the eastern Junggar Basin, Xinjiang, north-west China. It provides new insights into the reproductive diversification and phylogenetic relationships of lycopsids in the Late Devonian. The strobilus shares more characteristics with arborescent lycopsids than any herbaceous forms, and falls within the diagnosis of Lepidostrobus . Each sporophyll consists of a deltoid pedicel and a triangular lamina. Sporophylls are horizontally inserted into the strobilus axis in low spirals. The pedicel, with lateral alations and an abaxial keel, extends distally into the upturned lamina and downturned heel, producing a peltate appearance. A single sporangium with terminal longitudinal dehiscence is a radially elongate, dorsiventrally flattened ovoid and is attached along its length to the adaxial surface of the pedicel. A column-like subarchesporial pad is found in the sporangium. A possible ligule occurs on the adaxial surface of the pedicel distal to the sporangium. The strobilus is microsporangiate, containing Lycospora -type spores with granulate ornamentation and an equatorial flange. Based on this new species, the reproductive diversification and evolutionary pattern in arborescent lycopsids from the Devonian through the Carboniferous are discussed in a phylogenetic framework. We suggest that the reproductive strategies represented by bisporangiate- and monosporangiate-strobili had proliferated by the Late Devonian, which implies that phylogenetically advanced arborescent lycopsids bearing Lepidostrobus strobili had an earlier origin than previously thought.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143 , 55−67.     

Rodeites Sahni reinvestigated—I

A detailed investigation of Rodeites Sahni from nearly 100 specimens collected from the Deccan Intertrappean beds of India has brought to light some new important facts: (1) The sporocarp wall is thicker and the spores within it are larger than hitherto described. (2) The mode of sorus attachment, observed for the first time, is similar to that of Marsilea rather than Regnellidium. (3) The presence of a distinct cellular gametophyte inside some megaspores is an entirely new finding for the family Marsileaceae. The presence of a male prothallus inside smaller microspores is also newly observed. (4) The occurrence of sporocarps in groups and their attachment are unique. (5) The prismatic layer is distinct in the sporocarp wall of Rodeites The above observations help in reconsidering the position of Rodeites in the Marsileaceae.