Puertasaurus

Extinct genus of dinosaurs

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. The only species is Puertasaurus reuili. 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. It consists of four well preserved vertebrae, including one cervical, one dorsal, and two caudal vertebrae. Puertasaurus is a member of Titanosauria, the dominant group of sauropods during the Cretaceous. Puertasaurus was a very large animal. Its size is difficult to estimate due to the scarcity of its remains, but current estimates place it around long and in mass. The largest of the four preserved bones is the dorsal vertebra, which at wide is the broadest known vertebra of any sauropod. The Cerro Fortaleza Formation is of uncertain age, due to the inconsistency of stratigraphic nomenclature in Patagonia. When Puertasaurus was alive, the Cerro Fortaleza Formation would have been a humid, forested landscape. 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. The remains were recovered in Cerro Los Hornos, near the La Leona River, and were reported from the Cerro Fortaleza Formation (which, at the time, was referred to as the Pari Aike Formation). Novas estimated the new species was approximately long and weighing between This would place it as one of the largest dinosaurs, only rivaled in size by its relative Argentinosaurus, which has been estimated at up to in length and in mass. 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 long. In 2012, Thomas Holtz estimated Puertasaurus to have been potentially long and 72.5 80 tonnes (80 88 short tons). In 2013, the entire neck was estimated to have been approximately long by Mike Taylor and Matt Wedel. Later the same year, Scott Hartman made a reconstruction that suggests a total length of , slightly shorter than other estimates. In 2016, Gregory S. Paul estimated a length of and a weight of at least In 2017, paleontologist José Carballido and his colleagues estimated its mass at roughly , which was lighter than Patagotitan, a more complete giant sauropod.

Of the four vertebrae preserved in the holotype, the largest is the dorsal vertebra (thought to be a second dorsal vertebra), measuring tall and wide. This is the broadest sauropod vertebra known, and two thirds of its width is made up of the huge (structures projecting from the side of the vertebra), which are heavily expanded and have very deep bases, forming wing like structures when viewed from the front. In other titanosaurs, such as Dreadnoughtus, they are far less wide and deep. The zygapophyseal articulations, which connect two adjacent vertebrae, are located on the lower part the neural arch. The and (processes on the side of the vertebra) are strongly laterally projected. The cervical vertebra lacks (large cavities) and was not very pneumatic. The length of the restored centrum is estimated to be long based on other titanosaurs.

Puertasaurus is differentiated from other sauropods based on a unique combination of features. These features consist of the heavily expanded neural spines on the cervical vertebrae, which result in the neural spines being wider than the vertebral body, strong dorsolateral (high on the side) ridges on these neural spines, robust spinoprezygapophyseal laminae (projections in front of the neural spine) on the posterior cervical vertebrae, anterior dorsal vertebrae that are very short from front to back, and the animal's giant size.

Puertasaurus is from the Late Cretaceous Period of southern Patagonia. However, which formation it was derived from and its geological age have been disputed, because of the inconsistent stratigraphic nomenclature of southern Patagonia. It was originally reported as being from the Pari Aike Formation, and Maastrichtian in age. The Pari Aike Formation was subsequently reassigned to the Mata Amarilla Formation and reinterpreted as being from the Cenomanian to Santonian. The Cerro Fortaleza Formation represents a terrestrial ecosystem. The presence of paleosols and lignite suggests a humid environment with high amounts of rainfall and a high water table. Avulsion surfaces, histosols, carbonaceous fossil roots, and silicified wood all provide evidence of a low lying forested landscape with poor drainage. Non dinosaurian fauna known from the formation include crocodilians, turtles, bony fish, and lamniform sharks.