A new cordaitean pollen cone and pollen grains in situ from the Early Permian of Hexi Corridor and its geotectonic significance
A new species of cordaitean pollen cone is described and diagnosed from early Permian strata in Gansu Province, northwestern China. The gross morphology and well-preserved features of the species, named Cordaianthus yongchangensis Z. X. Wang et B. N. Sun sp. nov., have been studied in detail. The current fossil has helically arranged bracts and secondary fertile shoots. The bract, longer and wider than in other known fossils, diverges at approximately 90 from the axis; the secondary fertile shoots are obovate with scales on individual shoots, and fertile scales concentrated near the apex of the secondary fertile shoots. More than five pollen sacs are clustered on the fertile scales, which number 8-13. As the current species differs from any known species in the fossil records, it is considered as a new species of Cordaianthus. The species, with its microstructure of bracts and scales, in situ pollen sacs and pollen grains, provides important clues on the evolution of Cordaitopsida. Based on the known reproductive organs of cordaitean plants, we discovered that the current fossil, with its wide bracts that protect the helically arranged secondary fertile shoots, is similar to modern conifer cones, suggesting that the current fossil is an evolutionally advanced species. In comparisons with cordaitean fossils, the leaves of cordaitean plants from the ALT (Alashan Terrane) during the early Permian presented mixed leaf features of specimens from the NCB (North China Block) and SCB (South China Block). In conclusion, the ALT was already located between the NCB and SCB in the Early Permian. (C) 2016 Elsevier B.V. All rights reserved.