The Anatomy Of The Petrified Calamites Stem From The Late Permian In Guizhou And Yunnan Province

Calamites is the name of the large arborescent Equisetaceae plants, which is living in the late Paleozoic. It is the late Carboniferous to early Permian strata. It is an important coal-forming plant of the Carboniferous-Permian. Researches on calamites in the Euramerican flora are very deep and comprehensive, but in the Cathaysian flora, especially on its anatomical studies of stems are rare. The late Permian Xuanwei Formation of Panxian of Guizhou Province and Fuyuan of Yunnan Province in Southwest China produced abundant well-preserved fossil stems of calamites. This provides important information to understand the morphology, anatomy, phylogeny and evolution of Late Permian calamites. In this paper, peeling method and thin-section method widely used in the permineralized plant fossils are utilized. Detailed researches on the abundant permineralized calamitean stems collected from the upper Permian of Yunnan and Guizhou provinces are made and main achievements are as follows.Emendation on Arthropitys junlianensis made based on newly found specimens. The emended diagnosis is:The plant is macrophanerophytes, and the diameter of the stem can reach up to300mm. Pith consists of a large central cavity and narrow periphery which consists of isodiametric parenchymatous cells with lysigenous cavities and nests of secretory cells with black contents. Carinal canals are oval and small but clear. Carinal canals are surrounded on radial and internal sides by two to three layers of oval cells. Interfascicular rays disappear fast and no more than2mm in length. Secondary xylem is very thick and can be more than100mm. Secondary xylem can be divided into parenchymatous interfascicular zones that abruptly taper centrifugally and fascicular wedges of tracheids and secondary rays. The width of each fascicular wedge of tracheids is700μm (500μm—1000μm). Secondary rays are parenchymatous and narrow, usually uni-to biseriate. Secondary tracheids possess elongated scalariform thickenings on radial walls.A new conformis species:Arthropitys cf. A. yunnanensis is established. The diagnosis is:Plant is probably a small tree, with the diameter of more than100mm. Pith consists of isodiametric parenchymatous cells and a large cavity in the centre. Carinal canal were oval and clear. Carinal canal is surrounded by two to four layers of oval cells. Interfascicular rays extend from near the pith and become narrow quickly and very slender outwards to the periphery of secondary xylem. Secondary xylem is thick and divided into parenchymatous interfascicular zones (or primary rays) and fascicular wedges of tracheids and secondary rays. Primary rays abruptly taper centrifugally and some of them even can’t extend outwards through to the periphery of secondary xylem.The width of each secondary xylem strand is1000μm—1500μm. Secondary rays are parenchymatous and narrow, usually uni-to biseriate. Primary rays and secondary rays consist of parenchymatous cells with rectangular cross-sectional shape and isodiametric longitudinal section. Secondary tracheids possess elongated scalariform thickenings on radial walls. Cortex is developed, thick as5mm and divided into3parts. Leaf traces usually arranged in one ring near periphery of cortex.Relevant research of the three kinds of calamites stem which discovered from the upper Permian in Southwest China shows that they all have developed secondary xylem, which indicates that they may be macrophanerophytes or small trees. They had a wealth of individuals and may be the predominant in the vegetation of that time. They were distributed throughout the Southwest China, which means that they had a wide geographical distribution. They were adapted to a variety of ecological environments, not only on the beach or in water, but also in the high land or even on hills. Some specimens have clear growth ring, which in dicates a seasonal climate during that time in the area but not stable.