| La Amarga Formation | |
| Type: | Geological formation |
| Period: | Aptian |
| Age: | Barremian-Early Aptian ~ |
| Prilithology: | Sandstone |
| Otherlithology: | Mudstone |
| Namedfor: | La Amarga Arroyo |
| Namedby: | Musacchio |
| Year Ts: | 1970 |
| Region: | Río Negro, Mendoza & Neuquén Provinces |
| Country: | Argentina |
| Coordinates: | -39.6°N -70.2°W |
| Paleocoordinates: | -39.6°N -35.2°W |
| Unitof: | Rayoso Group |
| Subunits: | Puesto Antigual, Bañados de Caichigüe & Piedra Parada Members |
| Underlies: | Lohan Cura Formation |
| Overlies: | Agrio Formation |
| Thickness: | 160m (530feet) |
| Extent: | Neuquén Basin |
The La Amarga Formation is a geologic formation with outcrops in the Argentine provinces of Río Negro, Neuquén, and Mendoza. It is the oldest Cretaceous terrestrial formation in the Neuquén Basin.
The type locality is La Amarga Arroyo and China Muerta Hill.[1] The La Amarga Formation unconformably overlies the marine Agrio Formation of the Mendoza Group. It is in turn overlain by the Lohan Cura Formation, separated by another unconformity.
There are three members within the La Amarga Formation.
Most of the tetrapod fossils found in the La Amarga come from the Puesto Antigual Member.
| Dinosaurs | |||||
|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Images |
| Amargasaurus[2] | A. cazaui | Neuquén | Puesto Antigual | "Braincase and associated postcranial skeleton."[3] | |
| Amargatitanis | A. macni | Neuquén | Puesto Antigual | "Two caudal vertebrae, an incomplete right ischium, a right femur, an incomplete right tibia, an incomplete right fibula, a right astragalus, and an incomplete right metatarsal I." | |
| Ligabueino | L. andesi | Neuquén | Puesto Antigual | "A cervical neural arch, a mid to posterior dorsal neural arch, a posterior dorsal centrum, the left femur, left ilium, articulated pubic shafts, and two pedal phalanges."[4] | |
| Zapalasaurus | Z. bonapartei | Neuquén | Piedra Parada | ||
| Stegosauria indet. | Indeterminate | Neuquén | Puesto Antigual | "Supraorbital, cervical and caudal vertebrae, dermal armor".[5] [6] | |
| Other tetrapods | |||||
|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Images |
| Amargasuchus | A. minor | Neuquén | Puesto Antigual | A trematochampsid crocodylomorph, found in association with the holotype of Amargasaurus | |
| Pterosauria indet.[7] | Indeterminate | Neuquén | An isolated femur | ||
| Vincelestes | V. neuquenianus | Neuquén | Puesto Antigual | A cladotherian mammal | |