title: The earliest normal flower from Liaoning Province, China.
abstract: The early evolution of angiosperms has been a focus of intensive research for more than a century. The Yixian Formation in western Liaoning yields one of the earliest angiosperm macrofloras. Despite multitudes of angiosperm fossils uncovered, including Archaefructus and Sinocarpus, no bona fide normal flower has been dated to 125 Ma (mega-annum) or older. Here we report Callianthus dilae gen. et sp. nov. from the Yixian Formation (Early Cretaceous) in western Liaoning, China as the earliest normal flower known to date. The flower demonstrates a typical floral organization, including tepals, androecium, and gynoecium. The tepals are spatulate with parallel veins. The stamens have a slender filament, a globular anther, bristles at the anther apex, and in situ round-triangular pollen grains. The gynoecium is composed of two stylate carpels enclosed in a fleshy envelope, and develops into a "hip" when mature. Since the well-accepted history of angiosperms is not much longer than 125 Ma, Callianthus together with Chaoyangia, Archaefructus and Sinocarpus from the Yixian Formation demonstrate a surprisingly high diversity of angiosperms, implying a history of angiosperms much longer than currently accepted.
authors.affiliation: Nanjing Institute of Geology and Palaeontology, the Chinese Academy of Sciences, Nanjing, China. brandonhuijunwang@gmail.com
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Shaolin
authors.initials: S
authors.lastname: Zheng
mesh_terms: D005075:Biological Evolution; D002681:China; D035264:Flowers / Q000033:anatomy & histology* / Q000145:classification; D005580:Fossils; D019684:Magnoliopsida / Q000033:anatomy & histology* / Q000145:classification