Abstract: Study of gymnospermous pollen cones, identified with Sorosaccus gracilis Harris 1935, from the Yangcaogou Formation, Late Triassic of China, has led to the identification of new and significant characteristics of the species. The new specimens show distinct variations in the morphology of the distal laminar portions of the microsporophylls. These well- preserved fossils are helpful in elucidating, reconstructing and revising the diagnostic features of S. gracilis. After comparing the characteristics of the specimens from China with those of S. sibiricus Prynada 1962, and of the pollen cones which were respectively assigned to Baiera longifolia (Pom.) Heer 1876 from Siberia, Russia, S. minor Harris 1935 from Greenland, and S. umaltensis Krassilov 1972 from Bureya River of Russia, we consider that these four names should be reduced to the synonymy of S. gracilis. Thus we revise the diagnosis of Sorosaccus. The significance of Sorosaccus in evolution of pollen cones is discussed. We consider that Sorosaccus is possibly basic to the evolution of the genus Ginkgo by the reduction of the number of microsporangia and of microsporophylls. Ginkgo liaoningensis Liu, Crane, Li & Wang 2005 from the Early Cretaceous of Liaoning Province, China represents likely one of morphologically intermediate steps between Sorosaccus and G. biloba in evolution.

Key words: Sorosaccus gracilis, pollen cone, evolution