The fossil record of ornithischians in South America is sparse, and they are clearly underrepresented when compared with sauropod dinosaurs. However, recent discoveries indicate that ornithischians were more diversified than thought. The aim of the present contribution is to describe isolated remains belonging to ankylosaurs and ornithopods, including basal euiguanodontians and hadrosaurs coming from the Chorrillo Formation (upper Campanian–lower Maastrichtian), Santa Cruz province, southern Argentina. The fossil remains of ankylosaurs reported here are the southernmost recorded for the continent. They show a unique combination of plesiomorphic features, indicating that they may belong to a basal ankylosaur. Ankylosaurs and hadrosaurids are thought to have arrived in South America during the latest Cretaceous through Central America. However, a detailed overview of the fossil record of Gondwana indicates that both clades were present and probably diversified across southern continents. This indicates that their presence in South America may be alternatively interpreted as the result of migration from other landmasses, including Africa and Europe, or may even be the result of Jurassic–Early Cretaceous vicariance from their northern counterparts.

南美洲鸟臀目恐龙的化石记录稀少，与蜥脚类恐龙相比，它们的代表性明显不足。但是，最近的发现表明鸟类鸟类的多样性比想象的要多。本贡献的目的是描述属于甲龙类和鸟脚类动物的孤立遗骸，包括来自 Chorrillo 组（上坎帕阶–下马斯特里赫特），阿根廷南部圣克鲁斯省。这里报道的甲龙化石遗骸是该大陆最南端的记录。它们显示出独特的拟形特征组合，表明它们可能属于基部甲龙。甲龙和鸭嘴龙科被认为是在白垩纪晚期通过中美洲到达南美洲。然而，对冈瓦纳大陆化石记录的详细概述表明，这两个进化枝都存在并且可能在南部大陆上多样化。这表明它们在南美洲的存在可能被解释为从其他大陆（包括非洲和欧洲）迁移的结果，甚至可能是侏罗纪-早白垩世北部同类迁徙的结果。