Puertasaurus is a genus of sauropod dinosaur that lived in South America during the Late Cretaceous Period.

It is known from a single specimen recovered from sedimentary rocks of the Cerro Fortaleza Formation in southwestern Patagonia, Argentina, which probably is Campanian or Maastrichtian in age.

Described by the paleontologist Fernando Novas and colleagues in 2005, it was named in honor of Pablo Puerta and Santiago Reuil, who discovered and prepared the specimen.

The Cerro Fortaleza Formation is of uncertain age, due to the inconsistency of stratigraphic nomenclature in Patagonia.

Puertasaurus would have shared its habitat with other dinosaurs, including another large sauropod, Dreadnoughtus, in addition to other reptiles and fish.

The holotype and only known specimen of Puertasaurus reuili was discovered in the Santa Cruz Province of southern Patagonia, Argentina.

Puertasaurus reuilli was described by the paleontologists Fernando Novas, Leonardo Salgado, Jorge Calvo, and Federico Agnolin in 2005, and was named after the fossil hunters Pablo Puerta and Santiago Reuil, who discovered the holotype in January 2001 and prepared it afterwards.

[6][7] The discovery of the more complete Futalognkosaurus revealed that these previous estimates were likely too high, and suggested that giants such as Puertasaurus and Argentinosaurus were probably less than 33 meters (108 ft) long.

[8] In 2012, Thomas Holtz estimated Puertasaurus to have been potentially 30 meters (98 feet) long and 72.5-80 tonnes (80-88 short tons).

[9][10] In 2013, the entire neck was estimated to have been approximately 9 meters (30 feet) long by Mike Taylor and Matt Wedel.

[11] Later the same year, Scott Hartman made a reconstruction that suggests a total length of 27 meters (89 feet), slightly shorter than other estimates.

[14] In 2019, Gregory S. Paul estimated the mass of Puertasaurus to be in the size range of Patagotitan at 45–55 tonnes (50–61 short tons).

Hyposphene-hypantrum articulation (two structures on two vertebrae that fit into each other and form an extra joint) is not present, like other titanosaurs.

This, along with the expanded distal (front) end of the vertebra, provide evidence of powerful neck ligaments and muscles.

[20] More recent studies have stated that these deposits pertain to the Cerro Fortaleza Formation, which was dated to the Campanian or Maastrichtian (approximately 76 to 70 million years ago).

Avulsion surfaces, histosols, carbonaceous fossil roots, and silicified wood all provide evidence of a low-lying forested landscape with poor drainage.