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Patagotitan Temporal range: Albian
Reconstructed skeleton and fossils on display at the American Museum of Natural History, New York
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Clade:	†Macronaria
Clade:	†Titanosauria
Clade:	†Lognkosauria
Genus:	†Patagotitan Carballido et al., 2017
Type species
Patagotitan mayorum Carballido et al., 2017

Patagotitan is a genus of titanosaurian sauropod from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. It contains a single species, Patagotitan mayorum, first announced in 2014 and then validly named in 2017 by José Carballido, Diego Pol and colleagues.

Discovery

Femur

Remains of Patagotitan, a part of a lower thighbone, were initially discovered in 2008 by a farm laborer, Aurelio Hernández, in the desert near La Flecha, about 250 km (160 mi) west of Trelew. Excavation was done by palaeontologists from the Museum of Paleontology Egidio Feruglio. The lead scientists on the excavation were Jose Luis Carballido and Diego Pol, with partial funding from The Jurassic Foundation. Between January 2013 and February 2015 seven paleontological field expeditions were carried out to the La Flecha fossil site, recovering more than 200 fossils, both of sauropods and theropods (57 teeth). At least six partial skeletons, consisting of approximately 130 bones, were uncovered, making Patagotitan one of the most complete titanosaurs currently known.

The type species Patagotitan mayorum was named and described by José Luis Carballido, Diego Pol, Alejandro Otero, Ignacio Alejandro Cerda, Leonardo Salgado, Alberto Carlos Garrido, Jahandar Ramezani, Néstor Ruben Cúneo and Javier Marcelo Krause in 2017. 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.

Vertebra

The holotype, MPEF-PV 3400, was found in a layer of the Cerro Barcino Formation, dating from the latest Albian. The particular stratum has an age of 101.62 plus or minus 0.18 million years ago. The holotype consists of a partial skeleton lacking the skull. It contains three neck vertebrae, six back vertebrae, six front tail vertebrae, three chevrons, ribs, both breast bones, the right scapulocoracoid of the shoulder girdle, both pubic bones and both thighbones. 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. Specimen MPEF-PV 3399 is a second skeleton including six neck vertebrae, four back vertebrae, one front tail vertebra, sixteen rear tail vertebrae, ribs, chevrons, the left lower arm, both ischia, the left pubic bone and the left thighbone. Specimen MPEF-PV 3372 is a tooth. Specimen MPEF-PV 3393 is a rear tail vertebra. Specimen MPEF-PV 3395 is a left humerus as is specimen MPEF-PV 3396, while specimen MPEF-PV 3397 is a right humerus. Specimen MPEF-PV 3375 is a left thighbone while MPEF-PV 3394 is a right one. Specimens MPEF-PV 3391 and MPEF-PV3392 represent two calfbones.

The animals found, though excavated in a single quarry, did not all die at the same time. Within the 343 centimetre thick sediment containing the fossils, three distinct but closely spaced horizons correspond to three different burial events in which young adult individuals perished during floods. The water did not transport the carcasses any further but covered them with sandstone and mudstone. The animals were about the same size, differing no more than 5% in length. As far as can be ascertained, all bones discovered belong to the same species and are thus part of a monospecific assemblage.

Description

P. mayorum compared to a human.

P. mayorum has been estimated to have been 37 m (121 ft) long , with an approximate weight of 69 tonnes (76 tons). Initial estimates placed it at 40 m (131 ft) long with a weight of 77 tonnes (85 tons). This makes it comparable to the next largest titanosaur, Argentinosaurus (which has been estimated at 73–96.4 tonnes (80.5–106.3 tons) by some studies), and thus one of the largest land animals in Earth's history.

Front limb and shoulder blade at Museo Egidio Feruglio de Trelew, Chubut

The researchers who described the animal stated:

Given the size of these bones, which surpass any of the previously known giant animals, the new dinosaur is the largest animal known that walked on Earth.

Upon its initial discovery, science writer Brian Switek cautioned that it was too early to calculate the exact size of the dinosaur. Switek had said it may be revised to 33.5 m (110 ft) and 45.4 tonnes (50.0 tons).

Distinguishing traits

The authors indicated nine distinguishing traits of Patagotitan. The first three back vertebra have a lamina prezygodiapophysealis, a ridge running between the front articular process and the side process, that is vertical because the former process is situated considerably higher than the latter process. With the first two back vertebrae, the ridge running to below from the side front of the neural spine has a bulge at the underside. Secondary articulating processes of the hyposphene-hypantrum complex type are limited to the articulation between the third and fourth back vertebra. The middle and rear back vertebrae have vertical neural spines. In the first tail vertebra, the centrum or main vertebral body has a flat articulation facet in front and a convex facet at the rear. The front tail vertebrae have neural spines of which the transverse width is four to six times larger than their length measured from the front to the rear. The front tail vertebrae have neural spines that show some bifurcation. The upper arm bone has a distinct bulge on the rear outer side. The lower thighbone has a straight edge on the outer side.

Phylogeny

Chevrons and other bones

In 2017, Patagotitan was placed, within the Titanosauria, in the Eutitanosauria and more precisely the Lognkosauria, as a sister species of Argentinosaurus. Several subclades of the Titanosauria would have independently acquired a large body mass. One such event would have taken place at the base of the Notocolossus + Lognkosauria clade leading to a tripling of weight from maximal twenty to maximal sixty tonnes.

Eutitanosauria	Dreadnoughtus Lithostrotia Malawisaurus Baurutitan Nemegtosaurus Trigonosaurus Alamosaurus Opisthocoelicaudia Saltasaurus Neuquensaurus Rapetosaurus Isisaurus Tapuiasaurus Rinconsauria Rinconsaurus Muyelensaurus Aeolosaurus Overosaurus Bonitasaura Notocolossus Lognkosauria Mendozasaurus Futalognkosaurus Quetecsaurus Puertasaurus Drusilasaura Argentinosaurus Patagotitan

Paleoecology

Patagotitan lived during the Late Cretaceous period, between 95 and 100 million years ago, in what was then a forested region.The bearing sediments indicates that sedimentation took place with a low energy setting, related to floodplains of a meandering system (Carmona et al., 2016). A possible contemporary of Patagotitan, Giganototsaurus, was found in Paleosols (buried soil), siltstones, and claystones, some of which represent swamp conditions. A host of other possible contemporaries like Andesaurus, Buitreraptor and Limayasaurus were also found in the  Candeleros Formation, which represents an ancient braided river system. These would be consistent with the wet floodplain environment mentioned above.

Possible Contemporaries

• Giganotosaurus lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period, approximately 98 to 97 million years ago. The holotype specimen was discovered in the Candeleros Formation of Patagonia in 1993.
• Argentinosaurus (meaning "Argentine lizard") is a genus of titanosaur sauropod dinosaur first discovered by Guillermo Heredia in Argentina.The dinosaur lived on the then-island continent of South America somewhere between 97 and 93.5 million years ago, during the Late Cretaceous Period. It is among the largest known dinosaurs.
• Andesaurus is a genus of basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America.These fossils were discovered in the Candeleros Formation, dating to the Cenomanian stage of the Late Cretaceous period, about 99.6 to 97 million years ago.
• Buitreraptor is a predatory dromaeosaurid theropod dinosaur from the Cretaceous of Argentina.Four skeletons were found in 2004 in sandstone in Patagonia, Argentina during an excavation led by Sebastián Apesteguia and Peter Makovicky. Buitreraptor is from the early Late Cretaceous Candeleros Formation, dating to the Cenomanian-Turonian, about 94 million years ago.
• Rayososaurus is a genus of plant-eating sauropod dinosaur of the superfamily Diplodocoidea. It was found in the Rayoso Formation, in Patagonia, Argentina and lived about 99 million years ago (during the Early Cretaceous). The type species is R. agrionensis, named by Argentinian paleontologist José Bonaparte in 1996.
• Limaysaurus is a herbivorous rebbachisaurid sauropod dinosaur from the Lower Cretaceous of northwestern Patagonia. Limaysaurus was uncovered between 1995 and 2002 from the Puesto Quiroga Member of the Lohan Cura Formation at Cerro Aguada del León in the south-central part of Neuquén Province, Patagonia, Argentina.

Explanation

The presence of predator to take down prey is a well understood natural mechanism to prevent population explosion of herbivores. It follows that large prey will be accompanied by a proportionately large predator capable of taking it down.

The scattered remains of Argentinosaurus are "associated" with those of the 10-ton carnivore Giganotosaurus, meaning these two dinosaurs shared the same territory in middle Cretaceous South America. While there's no way even a desperately hungry Giganotosaurus could have taken down a full-grown Argentinosaurus all by itself, it's possible that these large theropods hunted in packs, thus leveling the odds. It is a reasonable deduction to state that Patagotitan may have shared a similar relationship with Giganotosaurus, given their proximity in time period and habitat. Up to 90% of predator-prey links involve a larger predator eating a smaller prey. This strengthens the notion that Giganotosaurus fed on juvenile Patagotitans.

Lastly, the above mentioned contemporaries gave been selected purely based on proximity to Patagotitan in terms of geography and time period. It is important to note that no formal research has yet been released/conducted in relation to Patagotitan on the above mentioned data. Hence, the data is at worst pure conjecture and at best a reasonable case of deductive reasoning.

External links

• Largest dinosaurs
• David Attenborough and the Giant Dinosaur, BBC