Ginkgoites manchurica from the Lower Cretaceous Shahezi Formation of Liaoning, China, and its palaeoclimate implications

The extreme greenhouse climate during the period of oceanic anoxic events (OAEs) in the Cretaceous is recognized based on marine stratigraphy, whereas the palaeoclimate remains poorly understood based on the terrestrial record due to the limitations of quantitative methods. The nearest living equivalent method, such as using the stomatal index of as a proxy, provides insight into reconstructing the terrestrial palaeoclimate during OAEs. However, due to the lack of well-preserved fossils with epidermal features and applicable quantitative methods, there are still controversies regarding the classification and nomenclature of species in the genus , which have been assigned to , , or . Here, we report well-preserved fossil leaves from the Lower Cretaceous Shahezi Formation in Changtu County, Liaoning Province, Northeast China. The fossil dry leaf mass per area (LMA) was estimated as a quantitative morphological and ecological proxy. The LMA results of 192–241 g/m for different specimens are very close, suggesting that these homonyms should be assigned to the same species. Therefore, combining the detailed epidermal features and a quantitative morphological proxy (LMA), we summarized and amended the previously described fossils into . Moreover, using the stomatal index of . , the palaeo-atmospheric CO concentration was calculated at 1270 ppmv using the Barclay SI-CO curve during the middle to late Aptian, indicating a typical greenhouse climate, which may be associated with the OAE global temperature increase event.