''Arackar'' (meaning "skeleton" in Kunza) is an extinct genus of

lithostrotia 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'' an ...

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

, possibly part of the

Saltasauridae Saltasauridae (named after the Salta region of Argentina where they were first found) is a family of armored herbivorous sauropods from the Upper Cretaceous. They are known from fossils found in South America, Africa, Asia, North America, and Eur ...

, discovered in the

Hornitos Formation The Hornitos Formation is a Campanian geologic formation of the Algarrobal Basin in the Atacama Region of northern Chile. The formation comprises limestones, sandstones, conglomerates, marls and tuff. Dinosaur remains are among the fossils that ...

Atacama Province Atacama Province () was one of the administrative divisions of Chile from 1843 to 1976. The capital was Copiapó. It was established on 31 October 1843 with its territory being carved out of the Province of Coquimbo. It was created as consequence ...

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

. The genus contains a single species, ''Arackar licanantay'', described by Rubilar-Rogers ''et al.'' in 2021.

Discovery and naming

The holotype was discovered in 1993 at Quebrada La Higuera, approximately 75 km (47 mi) south of

Copiapó Copiapó () is a List of cities in Chile, city and communes of Chile, commune in northern Chile, located about 65 kilometers east of the coastal List of towns in Chile, town of Caldera, Chile, Caldera. Founded on December 8, 1744, it is the capi ...

. The fossil material was briefly mentioned by Rubilar-Rogers & Gutstein in 2012 and was found to not be referable to the genus ''

Atacamatitan ''Atacamatitan'' (meaning "Atacama Desert titan") is a genus of titanosaurian sauropod dinosaurs from the Late Cretaceous Tolar Formation of Chile. Discovery and naming In February 2000, with the purpose of looking for Mesozoic fossils in Chi ...

''. In 2021, ''Arackar licanantay'' was named and described by David Rubilar-Rogers, Alexander O. Vargas, Bernardo González Riga, Sergio Soto-Acuña, Jhonatan Alarcón-Muñoz, José Iriarte-Díaz, Carlos Arévalo and Carolina S. Gutstein. The holotype, SNGM-1, was found in a layer of the

that dates back to the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

period (

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

stages). It includes vertebrae of the neck and back, as well as a

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

and

ischium The ischium (; : is ...

. It belonged to a juvenile and is currently the most complete specimen of a sauropod found in Chile. The full binomial name, ''Arackar licanantay,'' translates to "bones of the Atacamans" in the Kunza language.

Description

The holotype represents a small individual with a body length estimated at around long. The size of a fully grown ''Arackar'' is unknown. Some distinctive features have been identified by Ruilar-Rogers ''et al.''. The hollowing out between the front joint process and the vertebral body is high and wide. The hollowing out between the parapophysis and the lamina between the front joint process and the vertebral body extends over the entire front of the pedestal of the neural arch but not above the spinal canal. The posterior joint processes are narrower than the

neural spine Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

. The ridges between the neural spine and the posterior joint processes are reduced and shorter than the facet of the posterior joint process.

Classification

''Arackar'' was placed in the

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

within the

Lithostrotia 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'' an ...

in 2021, as a

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of ''

Isisaurus ''Isisaurus'' (named after the Indian Statistical Institute) is a genus of titanosaurian dinosaur from the Late Cretaceous Lameta Formation of India and Pab Formation of Pakistan. The genus contains a single species, ''Isisaurus colberti''. Di ...

''. Together, they form a sister

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

to ''

Rapetosaurus ''Rapetosaurus'' ( ) is a genus of titanosaurian sauropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period. Only one species, ''Rapetosaurus krausei'', has been identified. Like other sauropod ...

'', within the Lithostrotia. The cladogram from Rubilar-Rogers ''et al.'' (2021) is shown below:

References

{{Taxonbar, from=Q105745562 Titanosauria Dinosaur genera Campanian dinosaurs Maastrichtian dinosaurs Dinosaurs of South America Fossil taxa described in 2021