Angiosperms are the dominating plant group in current vegetation. They account for the majority of terrestrial primary production, demonstrate the highest diversity in the plant kingdom, and dominate highly diversified habitats [1-4]. The rapid radiation and diversification of angiosperms during the Cretaceous led to major ecological changes on the earth, the latter were a prerequisite for many critical evolutionary events [3] including the later evolution of human beings. However, the origin of this important plant group has remained obscure since the time of Darwin [3,5-8]. Although palaeobotanists have been searching for pre-Cretaceous angiosperms and some speculate that the angiosperm line may extend back to the Triassic [8,9], the earliest angiosperm fossil records are still restricted to the Cretaceous hitherto [3-5,10-12]. Therefore, it is not surprising that whenever something related to the origin of angiosperms is discovered, such as Sanmiguelia [13] and Archaefructus [6,7,14], it not only receives attention but also triggers controversy within and beyond academic circles. Western Liaoning has been a focus of palaeontological research because of its wealth of fossil plants [7,15-20] and animals [21,22]. Pan's claims of Jurassic angiosperms [15-17] once raised great interest in fossil plants in this region, but they are currently not generally accepted [18,23].
Schmeissneria was first identified as a member of the Ginkgoales [24], with a history dating back to 1838 [25]. Schmeissneria (Stachyopitys) was once thought to be related to conifers [25,26]. Its ginkgoalean affinity was initially proposed based on association: Schenk (1890) classified it as a premature male flower of Baiera, therefore placing Schmeissneria (Stachyopitys) in the Ginkgoales [27]. Based on the data available now, Schenk's conclusion on Schmeissneria (Stachyopitys) has been proven erroneous. First, the male nature of Schmeissneria (Stachyopitys) has been disproved [28]. Second, the connection between Baiera and Schmeissneria has been nullified [24,29]. Third, Schmeissneria has been proven connected with Glossophyllum? sp. A [30], which is dissimilar to any known ginkgoalean leaf [24]. All of this evidence refuted Schenk's initial proposal on the ginkgoalean affinity of Schmeissneria (Stachyopitys), and thus Schmeissneria lost its affinity. Apparently, Kirchner and Van Konijnenburg-Van Cittert did not realize what they had accomplished and conveniently put Schmeissneria in Ginkgoales [24]. In addition, there are a few characters that make Schmeissneria even more mysterious: 1) the internal structure of the reproductive organ, which is important for systematics, is hitherto unknown; 2) its connected vegetative parts do not provide enough information to resolve its systematic position; and 3) its winged seeds are never found in other Ginkgoales.
Here new specimens of Schmeissneria, S. sinensis Wang sp. nov., are reported from the Haifanggou Formation (middle Jurassic) in western Liaoning, China. The new information from these materials allowed us to re-examine the affinity of Schmeissneria.
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