DISCOVERY OF THE MIDDLE TRIASSIC CYCAD Nilssonia splendens IN BENXI CITY, LIAONING PROVINCE

Nilssonia Brongniart 1825 is one of representatives of Cycadophyta. It was widely distributed in China and the world through geological time. Recently, a pair of specimens of Nilssonia splendens Sun 1993 was discovered from the Middle Triassic Linjia Formation of Benxi, Liaoning in Northeast China. The species differentiates form other species of Nilssonia in their leaves with a slender rachis; veins generally without bifurcation, clear and thinner, slightly dense, closely to parallel, slightly upward curving to the apex, occurring at concentration of 28 per cm. Since N. splendens was first identified by Sun in 1993, the species has only been documented in the Upper Triassic in East Asia. The present specimens are the first record from the Middle Triassic. According to the present fossil specimens, and the transitional relationships of laminar segments and rachis from type specimens of Tianqiaoling in Jilin, China, the reconstruction of N. splendens was suggested. The origin and diffusion of N. splendens suggest that this species from the Middle Triassic Linjia Formation, not only enlarges the knowledge in taxonomy of Nilssonia, but also provides an opportunity to understand the evolution of Nilssonia in the mass extinction through the Permian-Triassic transition and its subsequent recovery in Northeast China.