In the Neuquén Basin, the Portezuelo Formation (Turonian-Coniacian, Upper Cretaceous) is represented by extended fluvial outcrops that are well-known for yielding an abundant and diversified vertebrate fossil record. However, most of the sauropod fossil record is represented by incomplete specimens, and only two taxa are formally described for the upper Turonian–lower Santonian of the Neuquén Basin: Malarguesaurus and Futalognkosaurus. In this contribution we report new sauropod specimens composed of partially associated axial and appendicular elements coming from the upper section of the Portezuelo Formation of the Los Bastos locality, in the southern Neuquén Basin. The bones show a set of morphological features that allow us to refer them to a titanosaur sauropod: a “cone-chisel-like” tooth, procoelic caudal vertebrae, a dorsally expanded ulna olecranon, and a femur with a prominent lateral bulge and an elliptical diaphysis in cross-section. The phylogenetic analysis recovers the sauropod remains as an unstable colossosaurian within Titanosauria, an effect likely attributable to the incomplete condition of the specimens. Nevertheless, osteological and phylogenetic analyses, together with morphological comparisons with the sauropod fossil record of the Portezuelo Formation, suggest that the new specimens represent a titanosaur different to previously known taxa. Pending better preserved and more complete remains from Los Bastos, the new evidence allows us to improve our knowledge of sauropod diversity during the upper Turonian–lower Santonian, at least in the southern Neuquén Basin.

在 Neuquén 盆地，Portezuelo 组（图隆阶-康尼亚阶，上白垩纪）以延伸的河流露头为代表，这些露头以产生丰富多样的脊椎动物化石记录而闻名。然而，大部分蜥脚类恐龙化石记录都由不完整的标本代表，内乌肯盆地的上图伦阶-下桑顿阶只有两个分类群被正式描述：马拉格龙和Futalognkosaurus. 在这篇文章中，我们报告了新的蜥脚类恐龙标本，它们由来自内乌肯盆地南部洛斯巴斯托斯地区 Portezuelo 组上部的部分相关的轴向和附肢元素组成。这些骨骼显示出一组形态特征，使我们能够将它们称为泰坦龙蜥脚类恐龙：“锥凿状”牙齿、前结肠尾椎骨、背部扩张的尺骨鹰嘴，以及具有突出侧凸和椭圆形的股骨横断面的骨干。系统发育分析发现，蜥脚类恐龙残骸是泰坦龙内不稳定的巨龙，这种影响可能归因于标本的不完整状况。尽管如此，骨学和系统发育分析，以及与 Portezuelo 组的蜥脚类恐龙化石记录的形态学比较，表明新标本代表了与以前已知的分类群不同的泰坦龙。等待洛斯巴斯托斯的更好保存和更完整的遗骸，新的证据使我们能够提高我们对上图伦阶 - 下桑托阶期间蜥脚类恐龙多样性的了解，至少在内乌肯盆地南部是这样。