重庆地区晚三叠世真蕨植物发育且类型丰富。本文报道了重庆云阳龙角镇须家河组第三段保存良好的真蕨植物化石标本。经详细的形态学研究和对比分析, 鉴定为Cladophlebis kwangyuanensis Li, 1964 (广元枝脉蕨)。该植物是在重庆云阳地区上三叠统中首次发现, 丰富了广元枝脉蕨的化石记录, 同时表明该属向四川盆地东部进一步扩展。结合伴生植物类型及数量和化石植物形态学特征(小羽片边缘锯齿明显, 叶质较薄, 叶脉羽状、稀疏而纤细), 认为云阳地区晚三叠世气候为温暖、潮湿的亚热带—热带季风气候。通过对四川盆地Cladophlebis的化石记录统计, 发现该属植物在三叠纪集中分布在四川盆地东缘。综合木化石年轮和古土壤的古气候重建结果表明, 在晚三叠世四川盆地东部受古特提斯洋水汽和东侧环太平洋海滨水汽的双重影响, 超强季风使得大量水汽进入盆地, 降雨量增加。因此, 盆地东部的气候条件非常适宜当时蕨类植物生长。

Pteridophytes are abundant in the Upper Triassic of Chongqing, southwestern China. Here we report specimens collected from the third member of the Upper Triassic Xujiahe Formation near Longjiao Town, Yunyang County of Chongqing. After detailed morphological study and comparison, these specimens are identified as Cladophlebis kwangyuanensis Li, 1964. These specimens represent the first occurrence of Cladophlebis kwangyuanensis Li, 1964 in the Upper Triassic in Yunyang, Chongqing. This report significantly expands the fossil record of Cladophlebis and indicates that the genus extended further east in the Sichuan Basin. Analysis of the distribution of published Cladophlebis records indicates that the Triassic Cladophlebis is concentrated in the eastern edge of the Sichuan Basin. Morphological characters of Cladophlebis kwangyuanensis, such as incised margin of pinnule, thin lamina, sparce and delicate pinnate veins, and the types and quantities of other associated plants, suggest that, during the Late Triassic in Yunyang area, this species lived in a warm, humid subtropical-tropical monsoon climate. These results, in combination with data of fossil wood growth rings and paleosoils, suggest that the east Sichuan Basin might have been influenced by the water vapors of the Paleo-Tethys Ocean and the eastern Pacific Rim during the Late Triassic. The strong monsoon brought water vapors into the basin increasing the rainfall and the climate conditions in the eastern area of the basin are suitable for the ferns to grow at that time.

重庆市自然科学基金面上项目(cstc2021jcyj-msmx0760)和国家自然科学基金青年项目(42102135)资助