Reassessment of Laplatasaurus araukanicus (Sauropoda: titanosauria), from the late cretaceous of Patagonia, Argentina

Abstract

The original materials assigned to Laplatasaurus araukanicus Huene 1929 comes from five different localities of northern Patagonia, ArgentineArgentina. These include several postcranial bones from multiple specimens and different conditions of preservation. The taxonomical status of the taxon worsens with the absence of quarry maps from any of the multiple localities (avoiding the recognition of associated materials), and a proper designation of type materials in its original description. After Huene, several new materials were assigned to this taxon, although dragging taxonomic problems. In 1979, the designation of a lectotype material (one tibia and one fibula) was the first stage for the establishment of the taxon validity and constituency. However, the validity of the remaining materials assigned to Laplatasaurus stayed unresolved. Here, we review all the materials that have hitherto been assigned to this taxon in order to establish a proper systematic status, to provide a re-description of the lectotype, to discuss the validity of materials previously referred to the genus, and to include it into an updated phylogenetic data matrix for the first time. Laplatasaurus araukanicus Huene 1929 is retained only for the lectotype material. The materials from Rancho de Ávila are referred to cf. Bonitasaura sp. by both stratigraphic congruence and presence of shared diagnostic features featuresshared with that titanosaur. The other remaining materials remains are referred as Lithostrotia indet. The A phylogenetic analysis nests Laplatasaurus within Titanosauria in a clade formed by ((Laplatasaurus + Uberabatitan) + (Bonitasaura + (Futalognkosaurus + Mendozasaurus)).