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Интеллектуальная Система Тематического Исследования НАукометрических данных |
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Mesopodial elements in hindlimbs of Ichthyosaurs and plesiosaurs: controversial Interpretations and Possible solutionтезисы доклада Тезисы
- Автор: Zverkov N.G.
- Сборник: 8th International Meeting on the Secondary Adaptation of Tetrapods to Life in Water
- Тезисы
- Год издания: 2017
- Место издания: Berlin, Museum für Naturkunde
- Первая страница: 39
- Последняя страница: 39
- Аннотация: The limbs of marine reptiles lack some function and characteristics essential for most amniotes: they do no more support body weight in terrestria l conditions but are modified into fins to steer or stabil ize underwater motion, and into fl ippers , primary propulsive organs. Thereby their structure was partially reorganized in order to serve new f unctions. ln some cases, this leads to ambiguous identifications of certain elements and makes the ir homologization problematic. The main controversy is the identification of mesopodial elements related to the emerge of 'neomorphic' ossicles in advanced ichthyosaurs and plesiosaurs. According to some researchers, the element located distal to the zeugopod ia and between them is the astragalus, whereas anterior to it the enlarged centrale emerges (e.g. Caldwe ll 1997a, b), or even the distal tarsal, shifted proximally to the tibia, fills the empty space anterior to the astragalus (e.g. McGowan and Motani 2003: p. 53). Others prefer to interpret the mesàpodial elements using amphibian-like pattern, thereby identifying a separated intermed ium and tibiale (e.g. Andrews 1910; McGowan and Motani 2003: p. 44). Recently published data on 're-evolution' of mesopodial elements in chameleons due to 'missing structures' (Diaz & Trainor 2015) could be successively appl ied for marine reptile tarsus. Thereby lacking of an astraga lus and evolving of an 'ancest ral' structu re convergent with amphibians seems to be preferable . This adaptation could be explained by strengthen ing of a leading edge of a limb in order to resist a hydrodynam ic loading, which is essential for basal aquat ic rept iles retaining the terrestrial hindlimb structure and lack ing ossifications in the anterior part of the mesopodium.
- Добавил в систему: Зверьков Николай Геннадьевич