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Ichthyosaurian relationships illuminated by new primitive skeletons from Japan

机译：鱼龙关系被日本新的原始骨架所照亮

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摘要

The Ichthyosauria is a group of reptiles with fish-shaped bodies from the Mesozoic (65-250 million years ago). Their secondary adaptations to aquatic life have obscured their ancestral features, and basal ichthyosaurs, which would be expected to retain these ancestral features (plesiomorphies), are poorly represented in the fossil record. As a result, their relationships to other amniotes have been controversial for over 180 years. New specimens of Utatsusaurus hataii from the Lower Triassic (240 Myr ago) of Japan are the first basal ichthyosaurs to show detailed features for almost the entire skeleton, including previously unknown parts of the skull and pelvic girdle. Compu-ter-assisted retrodeformation of fossil images shows that Utatsusaurus retained features of terrestrial amniotes in both the skull and the postcranial skeleton, such as the connection between the vertebral column and the pelvic girdle. Phylogenetic analyses indicate that ichthyosaurs belong in the Diapsida, but that, unlike the sauropterygians, they are not included with the Sauria (the crown group containing lizards, crocodiles, birds and Sphenodon). Recent studies have reported that the addition of ichthyosaurs to the amniote data altered the relationships among basal saurians, but no major clades were affected by the inclusion of ichthyosaurs in our analyses.
机译：鱼龙是由中生代（65-2.5亿年前）的鱼类形状的爬行动物组成的。它们对水生生物的二次适应已经掩盖了它们的祖先特征，而预计会保留这些祖先特征（多形性）的基底鱼龙在化石记录中的表现很差。结果，他们与其他羊膜的关系已引起争议超过180年。日本下三叠纪（240迈尔前）的新的哈达鱼鳞茎标本是首批显示几乎整个骨架（包括头骨和骨盆带未知部分）详细特征的基底鱼龙。计算机辅助化石图像的逆向变形显示，龙龙在头骨和颅后骨骼中都保留了陆地羊膜的特征，例如椎骨和骨盆带之间的连接。系统发育分析表明，鱼龙属属于蛇翅科，但与蜥脚类目动物不同，它们不属于蜥脚类动物（冠组中含有蜥蜴，鳄鱼，鸟类和剑齿龙）。最近的研究报告说，鱼龙到羊水数据中的添加改变了基础蜥蜴人之间的关系，但是在我们的分析中，没有主要进化枝受到鱼龙的影响。

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  • 来源
    《Nature》 |1998年第6682期|p.255-257|共3页
  • 作者

    Ryosuke Motani; Nachio Minoura; Tatsuro Ando;

  • 作者单位
  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自然科学总论;
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