A recent excavation yielded 118 large tridactyl footprints in the Lower Jurassic Dolomitic Formation of the Causses Basin, at Mongisty in southern France. Most of the tracks are ascribed to Eubrontes giganteus Hitchcock, 1845. They are preserved on a surface of 53 m2 and form parallel rows with a preferential orientation towards the north. Such an abundance and density of E. giganteus is observed for the first time in the Early Jurassic from the Causses Basin. Sedimentological and ichnotaphonomical analyses show that the footprints were made at different time intervals, thus excluding the passage of a large group. In contrast to all other tracksites from the Dolomitic Formation, where tracks are preserved in fine-grained sediments corresponding to low-energy depositional palaeoenvironments, the tracks from Mongisty are preserved in coarse-grained sediment which is a matrix- to clast-supported breccia. Clasts consist of angular to sub-rounded, millimetric to centimetric-scale (up to 2 cm), poorly sorted, randomly oriented, homogeneous dolostone intraclasts floating in a dolomudstone matrix. Sedimentological analysis shows that the depositional environments of Mongisty varied from subtidal to intertidal/supratidal settings in a large and protected flat marsh. The lithology of the track-bearing surfaces indicates that the mudflat of the Causses Basin was sporadically affected by large mud flows that reworked and redeposited mudstone intraclasts coming from the erosion of upstream, dry and partially lithified mud beds. Throughout the world, this type of preservation of dinosaur tracks in tidal matrix- to clast-supported breccias remains rare.

中文翻译：

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潮汐角砾岩中恐龙足迹的罕见保存：法国南部阿韦龙早期侏罗纪蒙吉斯蒂遗址的 Eubrontes giganteus

最近的一次挖掘工作在法国南部蒙吉斯蒂的 Causses 盆地的下侏罗统白云岩组中发现了 118 个大型三趾足印。大部分曲目归于大长虫希区柯克，1845 年。它们保存在 53 m 的表面上2并形成优先向北的平行行。如此丰富和密集的E. giganteus首次在早侏罗世从 Causses 盆地观察到。沉积学和 ichnotaphonomical 分析表明，足迹是在不同的时间间隔进行的，因此排除了一大群人的通过。与白云岩组的所有其他轨迹点相比，轨迹保存在与低能沉积古环境相对应的细粒沉积物中，Mongisty 的轨迹保存在粗粒沉积物中，这是一种基质到碎屑支撑的角砾岩。碎屑由角到亚圆形、毫米到厘米级（最大 2 厘米）、分选差、随机定向、均匀的白云岩内碎屑组成，漂浮在白云母岩基质中。沉积学分析表明，Mongisty 的沉积环境从潮下带变化到潮间带/潮上带环境，位于一个受保护的大型平坦沼泽地。履带支承面的岩性表明，Causses 盆地的泥滩偶尔受到大泥浆流的影响，这些泥浆流重新加工和重新沉积了上游、干燥和部分石化泥层侵蚀产生的泥岩内碎屑。在世界范围内，这种在潮汐基质到碎屑支撑的角砾岩中保存恐龙足迹的情况仍然很少见。