Temporal range: Albian
|Reconstructed skeleton on display at the Field Museum of Natural History, Chicago, IL|
Carballido et al., 2017
Carballido et al., 2017
Patagotitan is a genus of titanosaurian sauropod from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from multiple individuals: Patagotitan mayorum, first announced in 2014 and then validly named in 2017 by José Carballido, Diego Pol and colleagues. Contemporary studies estimated the length of the type specimen, a young adult, at 37 m (121 ft) with an approximate weight of 69 tonnes (76 tons).
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 (represented by 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.
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 one 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 burial events in which young adults perished due to 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.
Research as of 2017 estimated Patagotitan mayorum to have been 37 m (121 ft) long, with an approximate weight of 69 tonnes (76 tons). These findings represented a refinement of initial estimates that placed the taxon's adult size at 40 m (131 ft) long with a weight of 77 tonnes (85 tons); science writer Brian Switek had cautioned in 2014 that it was still too early to make size estimates with the desirable scientific certainty.
The Patagotitan taxon stands as readily comparable in size to the next largest titanosaur taxon, Argentinosaurus, 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.
Researchers who described Patagotitan 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.
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 front articular process is situated considerably higher than the side 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.
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.
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).
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