The herbivorous[2] Futalognkosaurus lived approximately 87 million years ago in the Portezuelo Formation, in what is now Argentina, of the Coniacian stage of the late Cretaceous Period.

Fossils of Futalognkosaurus were found in the Neuquén province of Argentina in 2000, and were scientifically described in 2007, alongside sauropods, Megaraptor, Unenlagia, iguanodonts, peirosaurids, and pterosaurs.

Due to its giant size the carcass likely acted as a barrier, altering the course of the river around it, lasting long enough for fish and bivalves to live in it, and eventually leaving an oxbow lake behind.

Its long neck contained 14 vertebrae, and was over a meter deep in places due to its extremely tall neural spines which had a distinctive "shark-fin" shape.

[11]In their phylogenetic analysis, Calvo and colleagues found Futalognkosaurus to be a member of the Titanosauridae (or Lithostrotia, depending on the definitions being used), and most closely related to Mendozasaurus.