The transitory dermal infoldings are described for the first time in front and behind the upper jaw in the larvae and postlarvae of the American paddlefish, Polyodon spathula Walbaum, 1858. In sturgeons these infoldings are necessary for the jaw protraction. In the paddlefishes, they, probably recapitulate the ancestral state. At the same time, the presence of these folds at the larval stages might indicate that the paddlefish larvae possess the protractive jaws. Further developmental studies of the jaw kinematics in Polyodon spathula are needed to test both hypotheses.

中文翻译：

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美国Pad鱼Polyodonspathula Walbaum（1858年，Acipenseriformes，Polyodontidae）的口腔用具中的临时皮肤褶皱。

首次在美洲pad鱼的幼虫和后幼虫的上颚的前部和后部首次描述了短暂的皮肤皱折，Polyodon spathula Walbaum，1858年。在st鱼中，这些皱折对于颌下垂是必需的。在the鱼中，它们可能概括了祖先状态。同时，在幼虫阶段存在这些褶皱可能表明鳞翅目幼虫具有长颚。为了进一步验证这两种假设，还需要对Polyodon spathula中的下颌运动学进行进一步的研究。