''Choconsaurus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of herbivorous sauropod

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

belonging to the group

Titanosauriformes Macronaria is a clade of sauropod dinosaurs. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (hence ...

, which lived in the area of present-day

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

at the end of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Discovery and naming

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

(specimen MMCh-PV 44/10) was found in

Villa El Chocón Villa El Chocón is a village and municipality in Neuquén Province in southwestern Argentina. The village was initially created to house the workmen building the Ezequiel Ramos Mexía dam (colloquially known as El Chocón Dam) on the Limay River. ...

in Neuquén province,

by Viviana Moro before 1996. Subsequent field campaigns carried out by the

Ernesto Bachmann Paleontological Museum The Ernesto Bachmann Paleontological Museum (''Museo Municipal Paleontológico, Arqueológico e Histórico "Ernesto Bachmann"'' or Archaeological, Paleontological and Historical Municipal Museum) (MEB) in Villa El Chocón, Neuquén Province, Arg ...

and the Museum of Geology and Paleontology of the National University of Comahue between 1996 and 2002 discovered more remains pertaining to ''Choconsaurus'', with several of the specimens described by Calvo (1999) under "

Titanosauridae Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Upchurch ''et al.'' in 2004 as the most recent common ancestor of '' Malawisaurus'' and '' Saltasaurus'' ...

indet.".Calvo, J.O. (1999). Dinosaurs and other vertebrates of the Lake Ezequiel Ramos Mexía Area, Neuquén, Patagonia, Argentina. ''National Museum Monographs'' 15: 13–45. In 2017, the species type ''Choconsaurus baileywillisi'' was named and described by Edith Simón, Leonardo Salgado and Jorge Orlando Calvo. The genus name refers to its discovery in El Chocón. For its part, the name of the species is in homage to the American geologist

Bailey Willis Bailey Willis (March 31, 1857 in Idle Wild-on-Hudson, New York, United States – February 19, 1949 in Palo Alto, California) was a geological engineer who worked for the United States Geological Survey (USGS), and lectured at two prominent Amer ...

, who traced the stratigraphy of the area between 1910 and 1914.

Description

The

specimen was found in a layer of the

Huincul Formation The Huincul Formation is a geologic formation of Late Cretaceous ( Early Cenomanian to Late Turonian) age of the Neuquén Basin that outcrops in the Mendoza, Río Negro and Neuquén Provinces of northern Patagonia, Argentina.

dating to the end of the Cenomanian epoch. It consists of a partial skeleton lacking a skull. The vertebrae of the neck, back and tail and parts of the limbs were preserved. This constitutes the most complete skeleton known of a basal titanosaur in 2017. The describing authors have identified some distinctive features. In the

cervical vertebra In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sa ...

e, the upper edge of the face of the posterior joint was hardly developed. In the first vertebrae there are very large secondary protuberances on both sides of the hyposphene. The central and posterior vertebrae have an additional crest located between the posterior crest that extends from the lateral protrusion to the vertebral body and the secondary crest running parallel to the main crest. The frontal vertebrae of the tail have a protrusion in the posterior hyposphenic secondary joint.

Classification

''Choconsaurus'' was classified in its description article of 2017 within the clade

Titanosauria Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thr ...

in a basal position, outside the clade

Eutitanosauria Eutitanosauria is a clade of titanosaurs, encompassing the more derived members of the group and characterized by the absence of the hyposphene-hypantrum articulation and possibly the presence of osteoderms. The group was first named by Sanz and ...

References

{{Taxonbar, from=Q41508018 Titanosaurs Cenomanian life Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Huincul Formation Fossil taxa described in 2017

Discovery and naming

Description

Classification

See also

References