Floral Evidence of Annonaceae from the Late Cretaceous of Japan
Floral Evidence of Annonaceae from the Late Cretaceous of Japan
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DOI：
10.1086/589693
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发表时间：
2008-09
影响因子：
2.3
通讯作者：
Masamichi Takahashi;E. M. Friis;K. Uesugi;Yoshio Suzuki;P. Crane
中科院分区：
文献类型：
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作者：
Masamichi Takahashi;E. M. Friis;K. Uesugi;Yoshio Suzuki;P. Crane
Futabanthus asamigawaensis gen. et sp. nov.是在日本本州岛东北部双叶群（早科尼亚世：晚白垩世）芦泽组（Asamigawa段）的上北叶地区发现的一种花化石。花小，有花梗，两性，辐射对称。花托扁平，盘状，花被下位，由少量花被片组成，至少两轮围绕边缘。雄蕊群由90-100个雄蕊组成，向花的中心弯曲。雄蕊粗壮，花药和花丝分化不明显。泡囊位于背轴的侧面，延伸到雄蕊的大部分长度，并具有侧向-外向开裂。药隔在囊上方膨大成一突出的、扁平的、不育的顶端附属物。雄蕊的药隔在雄蕊群上形成一个棋盘格状的保护表面。雌蕊群由约100-120个离生心皮组成，心皮长在花托中心的一个小的圆锥形突起上。化石花的多分裂结构，结合雄蕊的形式，表明与木兰目番荔枝科的关系。该化石目前提供了该科的最早记录，并记录了晚白垩世中期欧亚大陆东部番荔枝科的存在。
Futabanthus asamigawaensis gen. et sp. nov. is based on a single fossil flower from the Kamikitaba locality in the Ashizawa Formation (Asamigawa Member), Futaba Group (early Coniacian: Late Cretaceous), of northeastern Honshu, Japan. The flower is small, pedicellate, bisexual, and actinomorphic. The floral receptacle is flattened and disk shaped, with a hypogynous perianth consisting of a small number of tepals, borne in at least two cycles, around the rim. The androecium comprises ∼90–100 stamens that are curved toward the center of the flower. Stamens are stout, with no clear differentiation into anther and filament. The thecae are lateral to abaxial in position, extend for most of the length of the stamen, and have latrorse‐extrorse dehiscence. The connective is expanded above the thecae into a prominent, flattened, sterile apical appendage. Together, the connective extensions of the stamens form a tessellated protective surface over the androecium. The gynoecium is composed of ∼100–120 free carpels borne on a small, conical projection in the center of the receptacle. The multipartite construction of the fossil flower, combined with the form of the stamens, indicates a relationship to Annonaceae in the order Magnoliales. The fossil currently provides the earliest record of the family and documents the presence of Annonaceae in eastern Eurasia during the middle part of the Late Cretaceous.