ABSTRACT

The Middle Triassic was an important time in the evolutionary history of reptiles because it was during this time that many modern groups originated and initially diversified. In this context, the rich fossiliferous deposits of the Ladinian-age Erfurt Formation in southern Germany play an important role in elucidating reptilian diversity during this interval. Here we present an interesting record of a reptile with an unusual dentition. The material comprises a fragment of a left dentary. The teeth are tightly spaced and have chisel-shaped crowns, with the posterolingually extending apices abutting those of the successive teeth and forming a continuous cutting edge. Micro-computed tomography scanning of the jaw fragment revealed the teeth have expanded roots and sit on an open, shallow groove. The Meckelian canal is partially open lingually and a second canal for the inferior alveolar nerve and artery extends parallel to it. Although the preserved anatomical features of the material are insufficient for precise phylogenetic placement, the structure of the robust dentary and its teeth resembles those of some lepidosaurs and certain early Mesozoic marine diapsids. The distinctive morphology of the teeth, combined with the apparent lack of tooth wear, makes it difficult to assess their functional significance. It is interesting that extinct tetrapods with similar tooth morphologies come from strata representing freshwater and brackish-water paleoenvironments, which may serve as an additional line of evidence for future Morpho-functional assessments.

摘要

中三叠世是爬行动物进化史上的一个重要时期，因为正是在这个时期，许多现代群体起源并开始多样化。在这种情况下，德国南部拉丁时代 Erfurt 组丰富的化石沉积物在阐明这一时期的爬行动物多样性方面发挥了重要作用。在这里，我们展示了一个具有不寻常牙列的爬行动物的有趣记录。该材料包括左侧牙齿的碎片。牙齿间距紧密，有凿形牙冠，后舌延伸的牙尖与连续牙齿的牙尖邻接并形成连续的切削刃。颌骨碎片的显微计算机断层扫描显示牙齿已经扩大了牙根并位于一个开放的浅槽上。Meckelian 管在舌侧部分开放，下牙槽神经和动脉的第二个管与其平行延伸。尽管该材料保存的解剖特征不足以进行精确的系统发育定位，但坚固的牙齿及其牙齿的结构类似于某些鳞龙类和某些早期中生代海洋二肢类动物的结构。牙齿独特的形态，再加上明显没有牙齿磨损，很难评估它们的功能意义。有趣的是，具有相似牙齿形态的已灭绝四足动物来自代表淡水和咸水古环境的地层，这可能作为未来形态功能评估的额外证据。尽管该材料保存的解剖特征不足以进行精确的系统发育定位，但坚固的齿状结构及其牙齿的结构类似于某些鳞龙类和某些早期中生代海洋二肢类动物的结构。牙齿独特的形态，再加上明显没有牙齿磨损，很难评估它们的功能意义。有趣的是，具有相似牙齿形态的已灭绝四足动物来自代表淡水和咸水古环境的地层，这可能作为未来形态功能评估的额外证据。尽管该材料保存的解剖特征不足以进行精确的系统发育定位，但坚固的齿状结构及其牙齿的结构类似于某些鳞龙类和某些早期中生代海洋二肢类动物的结构。牙齿独特的形态，再加上明显没有牙齿磨损，很难评估它们的功能意义。有趣的是，具有相似牙齿形态的已灭绝四足动物来自代表淡水和咸水古环境的地层，这可能作为未来形态功能评估的额外证据。坚固的牙齿和牙齿的结构类似于一些鳞龙类和某些早期中生代海洋二肢类动物的结构。牙齿独特的形态，再加上明显没有牙齿磨损，很难评估它们的功能意义。有趣的是，具有相似牙齿形态的已灭绝四足动物来自代表淡水和咸水古环境的地层，这可能作为未来形态功能评估的额外证据。坚固的牙齿和牙齿的结构类似于一些鳞龙类和某些早期中生代海洋二肢类动物的结构。牙齿独特的形态，再加上明显没有牙齿磨损，很难评估它们的功能意义。有趣的是，具有相似牙齿形态的已灭绝四足动物来自代表淡水和咸水古环境的地层，这可能作为未来形态功能评估的额外证据。