梧桐属(Firmiana Marsili)约有16个现生种, 间断分布于亚洲东部和东南部以及非洲东部的热带至亚热带地区, 并在我国南北各省广泛栽培。其蓇葖果成熟后开裂, 开裂心皮呈叶状, 膜质, 易鉴别。该属果实化石非常匮乏, 迄今仅报道两例, 分别产自山东临朐的下中新统和云南临沧的上中新统。本文基于对产自山东临朐下中新统山旺组梧桐属蓇葖果化石的再观察, 发现2种梧桐属植物——Firmiana sinomiocenica Hu and Chaney和F. yunnanensis Xie and Manchester, 并对F. sinomiocenica的种征进行了修订。这些新材料表明中新世早期梧桐属在华东地区已经具有一定的多样性。Firmiana sinomiocenica与现生种F. simplex (L.) W. Wight最为相似, 可能指示F. simplex是梧桐属中比较原始的种类。Firmiana sinomiocenica的心皮和种子大小暗示, 在距今约17 Ma时, 梧桐属的染色体倍性可能已和现生的梧桐类似。值得注意的是, 梧桐属蓇葖果化石呈叶状, 可以借助风力传播。本文结合山旺植物群中其他翅果化石的研究, 认为果实的风力传播方式在该植物群中已经较为普遍。
Firmiana Marsili comprises ca. 16 species currently distributed in tropical to subtropical areas of eastern Africa and east-ern-southeastern Asia, and is widely cultivated in southern and northern China. Follicles of Firmiana are readily distin-guishable since they are dehiscent at maturity with dehiscent carpel foliate and membranous. However, follicle fossils of Firmiana are very rare and have been only known from the lower Miocene of Linqu, Shandong, East China and the upper Miocene of Lincang, Southwest China. Here we examine the follicle fossils of Firmiana from the lower Miocene Shanwang Formation of Linqu County, Shandong Province and find that the Miocene Shanwang flora includes two species of Firmi-ana—Firmiana sinomiocenica Hu and Chaney and F. yunnanensis Xie and Manchester. The specific diagnosis of F. sinomi-ocenica was emended based on the additional well-preserved seed-bearing fruit fossils. These new materials indicate that Firmiana already has a certain diversity in east China during the early Miocene. Firmiana sinomiocenica is the most similar to the living species F. simplex (L.) W. Wight in morphology, which suggests that F. simplex is a relatively primitive species in the genus. The sizes of carpels and seeds of F. sinomiocenica indicate that the chromosome ploidy of fossil Firmiana that occurred around 17 Ma was likely similar to that of extant F. simplex. Remarkably, the boat-like shape and membranous folli-cle favors wind dispersal. Together with other winged fruits, the Firmiana fossil fruits suggest that wind dispersal was well represented in the early Miocene Shanwang flora.