Geographic Variation in the Pes of the Salamander Hynobius lichenatus : A Comparison with Tetradactyl Hynobius hidamontanus and Pentadactyl Hynobius nigrescens

概要

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Variation in the pes was examined radiographically in 858 feet of three species of the genus Hynobius. The fifth toe of H. lichenatus was sometimes missing or barely expressed, caused by the absence of the fifth tarsale or by the fusion of the fourth and fifth tarsalia. Although the phalangeal formula was stable in H. hidamontanus (22320) and H. nigrescens (22332), it was highly variable in H. lichenatus (22332 and 31 other types were observed). In H. hidamontanus and some populations of H. lichenatus, there were unusual lots of feet with unossified first centrale and tibiale. Moreover, the unossification of the fifth tarsale, not influencing the occurrence of the fifth toe, was found in one population which corresponded to the southern limit of distribution of H. lichenatus. A postminimus (=extra ankle bone), occurring in some primitive tetrapods, appeared sporadically on the postaxial side in the tarsus of H. lichenatus and H. nigrescens, but not of H. hidamontanus. The complete absence of both the fifth toe and the postminimus, and the presence of only two centralia, due to the fusion of the second and third centralia, suggest that H. hidamontanus is one of the most derived groups among the Hynobius species.
社団法人日本動物学会の論文
1993-12-15