Puertasaurus was a large titanosaurid sauropod which lived during the late Cretaceous. It lived in what is now Patagonia, South America. The type species, Puertasaurs reuli, was named after Pablo Puerta and Santiago Reuil, who discovered the specimen in January 2001. It is based on a partial spinal column: a neck vertebra, a back vertebra, and two tail vertibrae.
At 30 m long, it was one of the biggest tinosaurs, in at around 73 tonnes it was one of the heaviest, too. However, the original estimates of 35–40 m and 80–100 tonnes, would place as the largest land animal to ever exist (aside from unconfirmed sauropods, like Amphicoelias). Its bones were recovered from the Pari Aike Formation, which is dated to be middle Cenomanian in age. It lived in what is now Patagonia. The type species, Puertasaurus reuili, is named in honor of Pablo Puerta and Santiago Reuil, who discovered the specimen in January 2001. Puertasaurus is based on a partial spinal column: a neck vertebra, a dorsal (back) vertebra, and two tail vertebrae. I
t's hunter was mainly a megaraptoran named Orkoraptor.
Of the four neck, back and tail vertebrae discovered, together forming the holotypeMPM 10002, the largest is the back vertebra, measuring 1.06 metres (3 ft 6 in) tall and 1.68 metres (5 ft 6 in) wide. This is the broadest sauropod vertebra known, and two-thirds of its width is made up of the huge wing-like diapophyses (side processes which supported the ribs), which are heavily buttresed and merge with both the centrum and the neural spine, forming a wide spade-like shape. In most sauropods, like Argentinosaurus, they are far less large, lack buttresses, and form a simple cross-bar shape. 
Fernando Novas, one of the paleontologists who described Puertasaurus reuili, estimated that the new species was approximately 35 to 40 metres (115 to 131 ft) long and weighed between 80 and 100 metric tons (88 and 110 short tons). This would place it as one of the biggest dinosaurs ever to walk the earth, only rivaled in size by its relative Argentinosaurus. More recent reconstructions suggest a length of 30 metres (98 feet) and a weight of 50 metric tons (55 short tons).Scott Hartman made a reconstruction that suggests a slightly shorter length of 27 metres (89 feet) and a total weight of 60–70 metric tons (66–77 short tons).
Puertasaurus belonged to the clade Titanosauria. It is closely related to the clade Lognkosauria, which includes the gigantic Futalognkosaurus and the somewhat smaller Mendozasaurus.
Puertasaurus is from the Late Cretaceous of southern Patagonia. However, what lithologic unit it was derived from and its geological age have been disputed. It was originally reported as being from the Pari Aike Formation, and Maastrichtian in age. These strata were subsequently reassigned to the Mata Amarilla Formation and reinterpreted as being from the Cenomanian to Santonian. However, stratigraphic nomenclature of southern Patagonia is inconsistent, and these deposits actually pertain to the Cerro Fortaleza Formation, which dates to the Campanian or Maastrichtian.