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

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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.