ZHENG Gaofeng,born in 1999,is a master student of School of Earth and Space Sciences,Peking University. He is mainly engaged in studies of Middle Devonian plants. E-mail: 2201210120@pku.edu.cn.
The plant fossils found in the Haikou Formation in Qujing,Yunnan Province,are typical representatives of the Middle Devonian southern Chinese flora. The plant assemblage is dominated by lycopsids plants,including a large number of endemic plants,known as the Haikou flora or Xichong flora. Based on new materials from the Middle Devonian Haikou Formation of Qujing,Yunnan Province,two lycopsid plants are described,namely Lepidodendropsis zhanyiense Zheng,Wang,Li,Liu et Xue sp. nov. and Minarodendron cathaysiense (Schweitzer et Cai)Li. Lepidodendropsis zhanyiense is characterized by simple leaf bases arranged in pseudowhorls,and its false leaf scars show as shallow furrows extending laterally on thin axes,but show as a more regular M-shaped structure on thick axes. Sterile leaves are undivided and linear in shape. Sporophylls are spoon-shaped and aggregated along fertile axes,forming an extended reproductive zone up to 18 cm long. Elliptical sporangia are borne on adaxial side of sporophylls. New material of Minarodendron cathaysiense displays similar morphology of axes and leaf bases as to those described in previous studies. Based on such new materials and as well as computer-aided modelling and taphonomic simulations,the morphological variations of leaf bases with false leaf scars are discussed,demonstrating that the M-shaped structures of Lepidodendropsis zhanyiense sp. nov. and other similar plants are probably not “leaf pits”as previously suggested. The Middle Devonian lycopsids shared similar,primitive leaf bases,and some types evolved large-bodied architecture e.g. tree habit,indicating their similar evolutionary grade in vegetative structures. The Middle Devonian lycopsid floras in South China are mainly distributed in fluvial and littoral facies and show a high degree of endemism,indicating the isolated geographic position of South China. The above results further enrich the plant diversity of the Middle Devonian in South China and provide new evidence for the evolution of lycopsids.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |