Polycotylids were a clade of short-necked plesiosaur that achieved a worldwide distribution and a peak of diversity during the Albian–Turonian, reaching the K/Pg mass extinction with a relative low diversity. One of the youngest polycotylids worldwide recorded is Sulcusuchus erraini, from Los Alamitos and La Colonia formations (Patagonia). Here, a new polycotylid specimen, also from Maastrichtian levels of the La Colonia Formation, is described; and the affinities of the new material and Sulcusuchus erraini are evaluated. Additionally, the phylogenetic position of Sulcusuchus erraini is reevaluated recovering Sulcusuchus erraini outside the Occultonectia, the latter comprising only Cenomanian–Turonian polycotylids. However, additional analysis indicate that the position of S. erraini is far from being well resolved.

多子叶动物是短颈蛇颈龙的一个进化枝，在阿尔比-图隆期间实现了全球分布和多样性的高峰，以相对较低的多样性达到了 K/Pg 大规模灭绝。世界记录的最年轻的多子叶植物之一是来自洛斯阿拉米托斯和拉科洛尼亚地层（巴塔哥尼亚）的 Sulcusuchus erraini 。在这里，描述了一个新的多子叶植物标本，同样来自拉科洛尼亚组的马斯特里赫特水平。并评估了新材料和Sulcusuchus erraini的亲和力。此外，重新评估了Sulcusuchus erraini 的系统发育位置以恢复Sulcusuchus erraini在 Occultonectia 之外，后者仅包含 Cenomanian-Turonian 多子叶植物。然而，额外的分析表明S的位置。erraini远未得到很好的解决。