论文标题：An unusual bird (Theropoda, Avialae) from the Early Cretaceous of Japan suggests complex evolutionary history of basal birds

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作者：Takuya Imai, Yoichi Azuma et.al

发表时间：2019/11/14

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本周An unusual bird (Theropoda, Avialae) from the Early Cretaceous of Japan suggests complex evolutionary history of basal birds手机版了一种在日本发现的此前未知鸟类物种的化石。这个物种生活在大约1.2亿年前的白垩纪早期，或能增进我们对于早期鸟类演化的理解。

Fukuipteryx prima复原图

图片来源：Masanori Yoshida

在德国发现的晚侏罗纪（约1.6亿-1.4亿年前）始祖鸟（Archaeopteryx）一般被认为是已知最早的鸟类，但是与现代鸟类相关的特征直到白垩纪才出现。已知最早的白垩纪鸟类化石是在明升中国东北地区发现的二维标本，它们缺少尾踪骨——一块位于脊椎末端的三角形骨头，用来支持尾羽，是现代鸟类的一个重要特征。

日本福井县立大学恐龙学研究所、福井县立博物馆的今井拓哉及同事描述了一块三维保存的鸟类化石，该化石与鸽子大小相当，发现于日本中部，可追溯至白垩纪早期。这块标本被命名为“Fukuipteryx prima”，是在明升中国以外发现的这一时期的第一个原始鸟类标本。作者认为F. prima可能和始祖鸟有若干相同的特征，包括结实的叉骨、未融合的骨盆和前肢，但是F. prima还拥有一个完全成形的尾踪骨。过去的研究已经表明，尾踪骨是鸟类在早期演化中关键的适应飞行的特征之一。但是，作者提出F. prima存在尾踪骨印证了一些新近的理论，即尾踪骨只是尾巴退化的副产物，与飞行适应无关。

摘要：The Early Cretaceous basal birds were known largely from just two-dimensionally preserved specimens from north-eastern China (Jehol Biota), which has hindered our understanding of the early evolution of birds. Here, we present a three-dimensionally-preserved skeleton (FPDM-V-9769) of a basal bird from the Early Cretaceous of Fukui, central Japan. Unique features in the pygostyle and humerus allow the assignment of FPDM-V-9769 to a new taxon, Fukuipteryx prima. FPDM-V-9769 exhibits a set of features comparable to that of other basalmost birds including Archaeopteryx. Osteohistological analyses indicate that FPDM-V-9769 is subadult. Phylogenetic analyses resolveF. prima as a non-ornithothoracine avialan basal to Jeholornis and outgroup of the Pygostylia. This phylogenetic result may imply a complex evolutionary history of basal birds. To our knowledge, FPDM-V-9769 represents the first record of the Early Cretaceous non-ornithothoracine avialan outside of the Jehol Biota and increases our understanding of their diversity and distribution during the time.

（来源：明升手机版(明升中国)）