# Huincul Formation

The Huincul Formation is a geologic formation of Late Cretaceous (Cenomanian to Early Turonian) age of the Neuquén Basin that outcrops in the Mendoza, Río Negro and Neuquén Provinces of northern Patagonia, Argentina. It is the second formation in the Río Limay Subgroup, the oldest subgroup within the Neuquén Group. Formerly that subgroup was treated as a formation, and the Huincul Formation was known as the Huincul Member.

## Description

The type locality of the Huincul Formation is near the town of Plaza Huincul in Neuquén Province after which the formation was named by Wichmann in 1929. This formation conformably overlies the Candeleros Formation, and it is in turn overlain by the Lisandro Formation.
The Huincul Formation is thought to represent an arid environment with ephemeral or seasonal streams. In some areas, it is up to 250 metres (820 ft) thick. It is mainly composed of green and yellow sandstones and can easily be differentiated from the overlying Lisandro Formation, which is red in color. The Candeleros Formation, underlying the Huincul, is composed of darker sediments, making all three formations easily distinguishable.

## Paleobiota

Dinosaur fossils are frequently found in the Huincul Formation. The titanosaurian sauropod Argentinosaurus huinculensis, one of the largest known land animals, is named after the formation. Another noteworthy Huincul dinosaur is the carcharodontosaurid theropod Mapusaurus roseae, which is regarded as one of the largest known terrestrial predators.

### Dinosaurs

Apart from sauropods and theropods, rare fossils of iguanodonts and other ornithopods have been recorded in the formation. Ichnofossils (footprints) of abelisaurid theropods and hadrosaurs are also known.

#### Ornithischians

| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. |
Ornithischians of the Huincul Formation :
| Taxa | Species | Locality | Stratigraphic unit | Material | Notes | Images |
| Chakisaurus | C. nekul | Pueblo Blanco Natural Reserve | Lower | Multiple partial skeletons belonging to individuals of different ages | An elasmarian ornithopod; the first ornithischian named from the Huincul Formation | |

#### Saurischians
##### Sauropods

| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. |
Sauropods of the Huincul Formation :
| Genus | Species | Locality | Stratigraphic unit | Material | Notes | Images |
| Argentinosaurus | A. huinculensis | Las Overas | | Seven dorsal vertebrae, partial sacrum, partial dorsal rib, fibula, and potentially other hindlimb bones | A titanosaur, sometimes considered the largest known sauropod | |
| Bustingorrytitan | B. shiva | Villa El Chocón. | Lower | Four specimens are known, including dentary and postcranial skeleton parts. | A titanosaur | |
| Cathartesaura | C. anaerobica | La Buitrera | Lower | A fossil consists of a partial skeleton including vertebrae and limb bones. | A rebbachisaurid | |
| Choconsaurus | C. baileywillisi | Villa El Chocón. | Lower | Partial skeleton without a skull, MMCh-PV 44/10. | A titanosaur | |
| Chucarosaurus | C. diripienda | Violante farm. | Lower | A complete left humerus, partial left radius, complete left metacarpal II, left ischium, partial left femur and fibula, partial right tibia, and partial indeterminate metapodial. | A titanosaur. | |
| Limaysaurus | L. tessonei | Villa El Chocón. | Lower | | A rebbachisaurid | Limaysaurus |
| Sidersaura | S. marae | Barda Atravesada de Las Campanas | Lower | Two partial skeletons consist of a braincase fused to the skull roof and partial neurocranium, partial dorsal vertebrae, a dorsal rib, two metacarpals, a partial pelvic girdle including an incomplete ilium, ischia, and pubes, and the left femur and fibula fourteen caudal vertebrae with some haemal arches, a partial left scapula, right pubic peduncle, part of both tibiae and fibulae, and several bones from the feet, including metatarsals, phalanges, and ungual phalanges. | A rebbachisaurid | |

##### Theropods

Theropods of the Huincul Formation :
| Taxa | Species | Locality | Stratigraphic unit | Material | Notes | Images |
| Aoniraptor | A. liberataem | Violante Farm | Lower | Sacral vertebra, six proximal caudal vertebrae, four mid-caudal vertebrae. | A fragmentary theropod originally described as a megaraptoran. | |
| Gualicho | G. shinyae | Violante Farm | Lower | A partial skeleton lacking the skull along with several veterbraes, ribs, the left shoulder girdle, the left forelimb, the right lower arm, the lower ends of both pubic bones, thighbones, shinbones, calf bones, metatarsi and three toes of the right foot (Holotype MPCN PV 0001). | A theropod of uncertain affinities | |
| Huinculsaurus | H. montesi | Aguada Grande | Upper | Several vertebrae | A noasaurid | |
| Ilokelesia | I. aguadagrandensis | Aguada Grande | Upper | Fragmented skull and the axial, appendicular skeleton. | An abelisaurid | Ilokelesia |
| Mapusaurus | M. roseae | | Upper (middle section of formation) | Multiple skeletal specimens. | A carcharodontosaurid | |
| Meraxes | M. gigas | Las Campanas Creek | Lower | A nearly complete skull, pectoral and pelvic elements, partial forelimbs, complete hindlimbs, fragmentary ribs, and cervical and dorsal vertebrae, a sacrum, and several complete caudal vertebrae. | A carcharodontosaurid | Meraxes gigas reconstruction |
| Overoraptor | O. chimentoi | Violante Farm | Lower | Skeletal specimen consists of two phalanges and a metacarpal of the right hand, two hemal arches, the right scapula, the right ulna, a partial ilium, a partial pubis, two metatarsals from each foot, and several phalanges and unguals from the left foot. | A paravian. | |
| Skorpiovenator | S. bustingorryi | Bustingorry's Farm | Lower | A preserved skeleton. | An abelisaurid | |
| Taurovenator | T. violantei | Violante Farm | Lower | An isolated right postorbital and a referred partial skeleton. | A carcharodontosaurid | |
| Tralkasaurus | T. cuyi | Violante Farm | Lower | An incomplete skeleton ( MPCA-Pv 815), which comprises a maxilla; dorsal, sacral, and caudal vertebrae; cervical ribs; and a badly-preserved pubis. | An abelisaurid | |

### Other reptiles

Apart from the taxa named here, fossils of unnamed squamates and neosuchian crocodyliforms have been discovered in the formation.
Non-dinosaur reptiles of the Huincul Formation :
| Genus | Species | Material | Notes |
| Kaikaifilusaurus | K. sp. | Incomplete right dentary | An eilenodontine rhynchocephalian |
| Patagosphenos | P. watuku | Disarticulated skull with shoulder and limb fragments | An eilenodontine rhynchocephalian |
| Prochelidella | P. buitreraensis | Skull, two cervical vertebrae, partial left forelimb, right pelvic girdle, shell fragments | A chelid turtle |