Two Late Cretaceous sauropods reveal titanosaurian dispersal across South America

E Martín Hechenleitner,Agustín G Martinelli,Sebastián Rocher,Lucas E Fiorelli,Léa Leuzinger,Leonardo Salgado,Jeremías R A Taborda

doi:10.1038/s42003-020-01338-w

Abstract

South American titanosaurians have been central to the study of the evolution of Cretaceous sauropod dinosaurs. Despite their remarkable diversity, the fragmentary condition of several taxa and the scarcity of records outside Patagonia and southwestern Brazil have hindered the study of continental-scale paleobiogeographic relationships. We describe two new Late Cretaceous titanosaurians from Quebrada de Santo Domingo (La Rioja, Argentina), which help to fill a gap between these main areas of the continent. Our phylogenetic analysis recovers both new species, and several Brazilian taxa, within Rinconsauria. The data suggest that, towards the end of the Cretaceous, this clade spread throughout southern South America. At the same locality, we discovered numerous accumulations of titanosaurian eggs, likely related to the new taxa. With eggs distributed in three levels along three kilometres, the new site is one of the largest ever found and provides further evidence of nesting site philopatry among Titanosauria.

Highlights

South American titanosaurians have been central to the study of the evolution of Cretaceous sauropod dinosaurs
We report the discovery of new dinosaurs from the Upper Cretaceous red beds of the Quebrada de Santo Domingo locality (QSD) in the Andes of La Rioja, NW Argentina (Fig. 1b)
Sandstone levels 170 m above the base of the Ciénaga del Río Huaco Formation (CampanianMaastrichtian) at QSD, La Rioja, NW Argentina (Geological Setting in Supplementary Information)

Summary

Introduction

South American titanosaurians have been central to the study of the evolution of Cretaceous sauropod dinosaurs Despite their remarkable diversity, the fragmentary condition of several taxa and the scarcity of records outside Patagonia and southwestern Brazil have hindered the study of continental-scale paleobiogeographic relationships. During the Late Cretaceous, they underwent an extensive evolutionary radiation worldwide Most of their record in South America is restricted to Argentine Patagonia (e.g., Neuquén, Golfo San Jorge and Austral basins) and the Bauru Basin of SW Brazil[7,8,9] (Fig. 1a). The results of our phylogenetic analysis incorporating the two new taxa suggest that they have Patagonian and Brazilian affinities, reinforcing the hypothesis of a close relationship between the titanosaurian sauropod faunas from northern and southern South America during the Late Cretaceous

Methods

Results

Conclusion