Paleontological and evolutionary developmental biological studies on body elongation, limb reduction and adaptive radiation in the evolution of lizards

(1)以鸟取群Kuwajima组发现的一种体型细长的小型爬行动物为基础，描述了一新属和新种Kaganaias hakusanensis。hakusanensis最有可能是dolicosauridae最基础的成员之一。hakusanensis是第一个在欧洲以外发现的化石，也是第一个出现在非海洋地层的化石。长龙是沧龙的姐妹类群，它们只在白垩纪中晚期的欧洲海洋沉积物中被发现。因此，人们认为各种各样的蜥蜴适应了白垩纪中期欧洲的海洋生活。一些系统发育假说认为，长颈龙不仅是沧龙的姐妹类群，也是蛇的姐妹类群，因此认为像蛇一样无肢的身体形式是由于适应水生环境而进化而来的。Kaganaias haskusanensis的发现不同意这些先前的假设。2)研究了六种不同种类蜥蜴的肢体发育，以便与发育阶段已确定的鸡进行比较。就肢体发育而言，发现一只孵化的蜥蜴惊人地处于相当于鸡的12^< >阶段的高级发育阶段。这种蜥蜴在孵化后进一步加速了四肢的发育。3)在Kuwajima组发现的厚舌鱼在形态上与来自欧洲的晚侏罗纪物种最相似，而一起发现的骨舌鱼是该群体最古老的化石记录。鱼类动物群展示了在Kuwajima组中发现的侏罗纪和白垩纪混合形式。它显示了与下孔类动物和恐龙相似的模式。这可能会为东亚这种时间混合的独特性提供支持。

1) A new genus and new species Kaganaias hakusanensis was described based upon a small reptile with the elongated body found in Kuwajima Formation, the Tetori Group. K.hakusanensis is most likely to be one of the most basal members of dolicosauridae. K.hakusanensis is the first fossil of the group found outside of Europe and also the first occurrence of a non-marine stratum. Dolichosaurs are sister groups of mosasaurs, and they are found only in the marine sediments deposited in Europe during mid to Late Cretaceous. It has been therefore believed that various lizards adapted to the life in the sea in Europe in mid Cretaceous. Some phylogenetic hypothese placed dolicosaurs as sister groups not only of mosasaurs but also of snakes, and thus argued that the snake like limbless body forms were evolved as the result of aquatic adaptation. The discovery of Kaganaias haskusanensis does not agree to these previous hypotheses. 2) Limb development of six different species of lizards was studied in order to make comparisons to that of chicken where developmental stages are well established. As far as limb development is concerned, a hatching lizard was found to be surprisingly in the advanced developmental stage equal to the 12^<th> stage in chicken. The lizard accelerated its limb development even further after hatching. 3) A pachycormid fish found in the Kuwajima Formation is morphologically most similar to a Late Jurassic species from Europe whereas an osteoglossid fish found together is the oldest fossil record of the group. The fish fauna exhibits the mixture of the Jurassic and Cretaceous forms found together in the Kuwajima Formation. It shows the similarity to the pattern seen in synapsids and dinosaurs. It may lend support for the uniqueness of this temporal mixture of East Asia.