Patagotitan is a genus of titanosaurian sauropod dinosaur from the Early Cretaceous (Albian stage) Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from at least six young adult individuals, Patagotitan mayorum, which was first announced in 2014 and then named in 2017 by José Carballido and colleagues. Originally thought to be the largest known titanosaur and land animal overall, preliminary studies and press releases suggested that Patagotitan had an estimated length of and an estimated weight of . Later research revised the length estimate down to and weight estimates down to approximately , suggesting that Patagotitan was of a similar size to, if not smaller than, its closest relatives Argentinosaurus and Puertasaurus. Still, Patagotitan is one of the best-known titanosaurs, and so its interrelationships with other titanosaurs have been relatively consistent in phylogenetic analyses. This led to its use in a re-definition of the group Colossosauria by Carballido and colleagues in 2022.
Like Argentinosaurus and other members of its clade, Lognkosauria, Patagotitan was a particularly large and robust titanosaur. It can be distinguished from its close relatives by a suite of unique characteristics in its and , and in the forelimb, and and in the hindlimb. Among these was the presence of accessory vertebral articulations known as the between only one pair of vertebrae at the level of the scapular blade, which was likely a weight-bearing adaptation not seen in any other sauropod (where they were either present between all pairs or between none). Several unique features in the limbs were also likely attachment scars for muscles. In life, Patagotitan lived in a forested region on a floodplain that was dominated by coniferous trees.
Discovery
A part of a lower was discovered in 2010 by a farm laborer, Aurelio Hernández, in the desert near La Flecha, Argentina, about west of Trelew. This discovery was reported to P. Huerta at the Museum of Paleontology Egidio Feruglio (MPEF) in Trelew. One preliminary field expedition to the La Flecha site was carried out in late 2012 by the MPEF, followed by seven further expeditions that discovered new fossils between January 2013 and February 2015. The lead scientists on the excavation were Jose Luis Carballido and Diego Pol, with partial funding from The Jurassic Foundation. More than 200 fossils, including 130 sauropod bones and 57 theropod teeth, were uncovered. The rock layers at the La Flecha site belong to the Cerro Castaño Member of the Cerro Barcino Formation, and were specifically dated to approximately 101.62 million years in age (corresponding to the latest Albian age of the Cretaceous).
The collected sauropod fossils were organized into six partial skeletons, which likely belonged to the same species due to uniformity in their morphology and size (with all individuals differing no more than 5% in length). Although the remains all came from the same quarry, the individuals likely did not all die at the same time. Within the sediment layer containing the fossils, there are three distinct but closely-spaced levels corresponding to three burial events, which are named FLV1, FLV2, and FLV3. One skeleton from FLV3 was designated as the holotype specimen of a new species, and was catalogued as MPEF-PV 3400. It consists of a partial skeleton lacking the skull, with three , six , six front , three , , both plates of the sternum and the right in the shoulder girdle, both , and both femora. The skeleton was chosen to be the holotype because it was the best preserved and also the one showing the most distinguishing traits.
Other specimens were designated as the paratypes. Based on overlapping elements, these include at least three individuals from FLV1, one from FLV2, and one from FLV3 other than the holotype. MPEF-PV 3399 (from FLV1) is a second skeleton consisting of six neck vertebrae, four back vertebrae, one front tail vertebra, sixteen rear tail vertebrae, ribs, chevrons, the left and , both , the left pubic bone, and the left femur. MPEF-PV 3372 (from FLV1) is a tooth. MPEF-PV 3393 (not associated with a layer) is a rear tail vertebra. MPEF-PV 3395 and MPEV-PV 3396 (both from FLV1) are left , while MPEF-PV 3397 (from FLV2) is a right humerus. MPEF-PV 3375 (FLV3) is a left femur while MPEF-PV 3394 (FLV1) is a right femur. MPEF-PV 3391 and MPEF-PV 3392 (both from FLV1) represent two . Another quarry was excavated about west, revealing a fourth sediment layer (FLV4) with a similarly sized sauropod skeleton.
In 2017, José Luis Carballido, Diego Pol, Alejandro Otero, Ignacio Alejandro Cerda, Leonardo Salgado, Alberto Carlos Garrido, Jahandar Ramezani, Néstor Ruben Cúneo and Javier Marcelo Krause named these remains as the type species of a new genus, Patagotitan mayorum. Collectively, the known remains made Patagotitan one of the most completely-known members of the Titanosauria. The generic name combines a reference to Patagonia with a Greek Titan for the "strength and large size" of this titanosaur. The specific name honours the Mayo family, owners of La Flecha ranch.
In 2019, Carballido and Pol published Titanosaur, a children's book with illustrations by Florencia Gigena. The book tells the story of their La Flecha fossil dig in scientific detail and is intended to inspire young paleontologists.
Exhibits
Skeletal mounts based on all available material of Patagotitan are displayed in multiple museums. Research Casting International digitally scanned the specimens, which was followed by the creation of foam molds, fiberglass casts, and 3D printing. One mount is exhibited in the Museum of Paleontology Egidio Feruglio. Another is exhibited in the American Museum of Natural History, where it replaced a juvenile Barosaurus mount. Some of the original fossils, including a femur, were also on display briefly. One is exhibited in the Field Museum of Natural History, where it replaced the Sue specimen of Tyrannosaurus (which has been moved to another exhibit). From March 2023 until January 2024, one was displayed at the Natural History Museum, London.
Description Size
Like other titanosaur sauropods, Patagotitan was a quadrupedal herbivore with a long neck and tail and is notable for its large size. Carballido and colleagues stated in the media:
In 2014 news reports provided estimates of Patagotitan size at long with a weight of . In 2017, Carballido and colleagues published a length estimate of , and provided two weight estimates: using a scaling equation, and using volumetric method based on 3D skeletal models. These estimates suggested that Patagotitan was 10% larger than Argentinosaurus. In 2019 Gregory S. Paul estimated Patagotitan at in length and in weight using volumetric models. This made it smaller than Argentinosaurus, which he estimated at over in length and in weight. In 2020, Campione and Evans yielded a body mass estimate of approximately . In 2020, Otero and Carballido published a lower mean weight estimate of using a revised scaling equation, with a margin of error of ; this was close to the 2017 volumetric estimate. Histology of five femora and one humerus indicates that the individuals died while they were young adults, with growth having slowed but not ceased entirely. In 2024, Paul estimated its length at , and its weight at .Paul, G.S. (2024) The Princeton Field Guide to Dinosaurs. 3nd ed. Princeton University Press p. 257 In 2025, Matthew Dempsey estimated Patagotitan weight at over .
Following the initial publication of Patagotitan in 2017, science writer Riley Black and paleontologist Matt Wedel cautioned against the reported estimates. In blog posts, Wedel noted that based on available measurements Patagotitan was comparable in size with other known giant titanosaurs. However, almost every measurement that could be compared was larger in Argentinosaurus. Wedel also criticised the polygon-based method that Carballido and colleagues used to compare the sizes of Patagotitan and Argentinosaurus vertebrae, noting that the former was largely empty space. In other studies, Argentinosaurus has been estimated at . In 2019, Paul noted that the articulated length of the back vertebrae was larger in Argentinosaurus () than in Patagotitan (), making it impossible for Patagotitan to have had a larger torso. For Patagotitan to have been larger, he reasoned that the rest of its body would have to have been improbably large, or vice versa in Argentinosaurus. He attributed this conclusion to a lack of proper measurement techniques. Also, he criticized the 3D model used for the volumetric estimate as having a flat-sided torso, and noted that the neck and tail were reconstructed as being fairly long.
Vertebrae
The vertebrae in the front and middle portions of the neck of Patagotitan were very long, being at least five times as long as they were wide at the back, with on top that were horizontally flattened, and only small holes and no large (neurovascular openings) on the sides. By contrast, the rear neck vertebrae of Patagotitan had deep pleurocoels that opened from the sides into the interior of the bone; whether the neural spines of these vertebrae were horizontally expanded as in Futalognkosaurus, Ligabuesaurus, and Mendozasaurus cannot be determined.
Like Futalognkosaurus and other titanosaurs that preserved a complete set of back vertebrae, Patagotitan probably had 10. Several characteristics in the back vertebrae distinguished Patagotitan from other titanosaurs. The , ridges of bone crossing the vertebrae, were thin and strongly developed in the back vertebrae of Patagotitan, unlike Argentinosaurus and Puertasaurus. Uniquely, the prezygodiapophyseal laminae (PRDLs, which ran between , from the at the front to the at the sides) were nearly vertical because the prezygapophyses were situated higher up on the vertebrae than the diapophyses. The PRDLs usually instead extended forward from the diapophyses in other sauropods. All of the neural spines in the back were tall and vertical in Patagotitan, and the first few had expanded, arrow-shaped ends. Argentinosaurus had front neural spines with arrow-shaped ends, but like other members of the Titanosauriformes the rear neural spines were inclined backwards; Patagotitan represents a reversal to the condition in non-titanosauriforms. Dreadnoughtus, Puertasaurus, and other members of the Lognkosauria had short front neural spines lacking the arrow-shaped ends. Uniquely, in the first two back vertebrae, the prespinal laminae that ran alongside the front of the neural spines bulged outwards near the bottom. Also uniquely, the third back vertebra preserves a at the rear end but not a at the front; the missing fourth back vertebra presumably had a corresponding hypantrum. Hyposphene-hypantrum articulations to stiffen the vertebrae were primitively present among sauropods and lost multiple times, but Patagotitan is the first known sauropod where they were retained between only one pair of vertebrae. Because the shoulder blade was located at this position, this may have been a weight-bearing adaptation.