Allen Formation | |
---|---|
Stratigraphic range: Mid Campanian-Maastrichtian ~ | |
Type | Geological formation |
Unit of | Malargüe Group |
Underlies | Jagüel Formation |
Overlies | Anacleto Formation |
Thickness | up to 70 m (230 ft) |
Lithology | |
Primary | Mudstone, sandstone |
Other | Limestone |
Location | |
Coordinates | 40°00′S66°36′W / 40.0°S 66.6°W |
Approximate paleocoordinates | 42°48′S52°12′W / 42.8°S 52.2°W |
Region | Neuquén, Río Negro & La Pampa Provinces |
Country | Argentina |
Extent | Neuquén Basin |
Type section | |
Named by | Uliana & Dellapé |
Year defined | 1981 |
The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous (middle Campanian to early Maastrichtian. [1] Dinosaur remains are among the fossils that have been recovered from the formation. [2] Indeterminate chelid remains and other vertebrates have also been discovered in this formation. [3]
The stratotype of the formation was defined by Uliana and Dellapé in 1981 in the eastern area of the Bajo de Añelo, where the relation between base and top is clearly exposed. The deposits are mostly clastic, interbedded with banks of limestone and layers of anhydrite, which were defined continental and shallow marine facies associated with semiarid conditions. [4]
The interpreted sedimentary paleoenvironments range from purely continental such as ephemeral lacustrine, aeolian and fluvial systems to coastal marine paleoenvironments with development of estuaries and tidal flats, followed by a lagoon sedimentary stage from marsh to sea with carbonate precipitation in an area protected from waves, ending with a retraction leading to the accumulation of evaporites. [4]
A detailed facies analysis of the formation was performed by Armas and Sánchez in 2015, where the authors concluded the formation represents a hybrid coastal system of tidal flats, dominated by Atlantic ingressions, with a large storm influence in some areas linked to aeolian systems. [5]
Dinosaur eggs are known from the formation. [6]
Ankylosaurs reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Patagopelta | P. cristata | Lower | Tooth, three posterior dorsal vertebrae, caudal vertebrae, two caudal centra, right femur, partial cervical half ring, and osteoderms. |
Hadrosaurs reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Bonapartesaurus | B. rionegrensis | Lower | ||||
Kelumapusaura | K. machi | Upper | Partial skull, a cervical vertebrae, several sacrals, sternal rib and sternal plate and multiple referred specimens found in a bonebed | |||
Lapampasaurus | L. cholinoi | Lower | Elements of the axial and appendicular skeleton of a subadult individual | |||
Willinakaqe | W. salitralensis | Lower |
Sauropods reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Aeolosaurus | Indeterminate | Lower | ||||
B.reigi [12] | Río Negro Province [12] | Lower | Braincases, caudal vertebrae, and several limb elements | |||
Menucocelsior | M. arriagadai | Lower | Seventeen caudal vertebrae and several appendicular bones: a right humerus, a left fibula and some metapodial. | |||
Panamericansaurus | P. schroederi | "Five tail vertebrata, sacral vertebrae, left humerus and rib fragments" | ||||
Pellegrinisaurus? | P. powelli | Lower (if it is from the formation) | "Dorsal and caudal vertebrae, partial femur" | |||
Rocasaurus | R. muniozi | Lower | "Partial postcranial skeleton" |
Theropods reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Austroraptor | A. cabazai | Lower | A fragmentary skeleton including parts of the skull, lower jaw, a few neck and torso vertebrae, some ribs, a humerus, and assorted bones from both legs | A dromaeosaurid. | ||
Bonapartenykus | B. ultimus | Upper | ||||
Lamarqueavis | L. australis | Lower | "Right coracoid with damaged sternal and omal extremities, and lacking acrocoracoidal process" | A prehistoric bird. | ||
Limenavis | L. patagonica | Lower | "Partial forelimb" | A prehistoric bird. | ||
Niebla | N. antiqua | Upper | Braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs, and incomplete vertebrae. | An abelisaurid [18] | ||
Quilmesaurus | Q. curriei | Upper | Femur and distal tibia | An abelisaurid. |
Fragmentary fossils are known from the formation. [6]
Pterosaurs reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Aerotitan | A. sudamericanus | Bajo de Arriagada | Uppermost Allen Fm. | Partial rostrum | The first unambiguous azhdarchid from South-America [20] | |
Fish reported from the Allen Formation [3] | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Diplomystidae | indeterminate | 4 incomplete pectoral spines | ||||
Siluriformes | indeterminate | 5 incomplete pectoral spines | ||||
Lepisosteidae | indeterminate | 6 vertebral centra | ||||
Teleostei | indeterminate | 10 isolated teeth | ||||
cf. Percichthyidae | indeterminate | 19 fragmentary vertebrae | ||||
Ceratodontiformes | indeterminate | 3 tooth plates | ||||
Chondrichthyes | indeterminate | 11 vertebral centra | ||||
Squamates reported from the Allen Formation [3] | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Patagoniophis | P. parvus | incomplete trunk vertebra | ||||
Alamitophis | A. argentinus | incomplete trunk vertebra | ||||
Madtsoiidae | indeterminate | incomplete trunk vertebra | ||||
Rhynchocephalia reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Lamarquesaurus | L. cabazai | Cerro Tortuga | [21] | |||
Plesiosaurs reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Kawanectes | K. lafquenianum | |||||
Unnamed frogs belonging to the family Calyptocephalellidae and Leptodactylidae, and those with no family designation were also found. [22] [3]
Frogs reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Kuruleufenia | K. xenopoides | Pipid frog. [23] | ||||
The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species. [24]
Mammals reported from the Allen Formation | |||||
---|---|---|---|---|---|
Genus | Species | Location | Material | Notes | Images |
Mesungulatum | M. lamarquensis | Cerro Tortuga | Two upper molars and a fragmentary lower molar | A dryolestoid | |
Groebertherium | G. stipanicici | Cerro Tortuga | One upper molar | A dryolestoid | |
cf. Brandonia | sp. | Cerro Tortuga | One lower molar | A dryolestoid | |
Barberenia | B. allenensis | Cerro Tortuga | One upper molariform | A dryolestoid | |
Trapalcotherium | T. matuastensis | Cerro Tortuga | One first lower molar | A gondwanathere | |
Plants reported from the Allen Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Podocarpoxylon | P. mazzonii | Valcheta Petrified Forest, Río Negro Province. [25] | Fossil wood. [25] | |||
Bonitasaura is a titanosaurian dinosaur hailing from uppermost layers of the Late Cretaceous (Santonian) Bajo de la Carpa Formation, Neuquén Group of the eastern Neuquén Basin, located in Río Negro Province, Northwestern Patagonia, Argentina. The remains, consisting of a partial sub-adult skeleton jumbled in a small area of fluvial sandstone, including lower jaw with teeth, partial vertebrae series and limb bones, were described by Sebastian Apesteguía in 2004.
Quilmesaurus is a genus of carnivorous abelisaurid theropod dinosaur from the Patagonian Upper Cretaceous of Argentina. It was a member of Abelisauridae, closely related to genera such as Carnotaurus. The only known remains of this genus are leg bones which share certain similarities to a variety of abelisaurids. However, these bones lack unique features, which may render Quilmesaurus a nomen vanum.
Anabisetia is a genus of ornithopod dinosaur from the Late Cretaceous Period of Patagonia, South America. It was a small bipedal herbivore, around 2 metres long.
Patagonykus is a genus of theropod dinosaur from the Upper Cretaceous of Argentina. This alvarezsauroid was discovered in exposures of the Portezuelo Formation (Turonian-Coniacian) of the Rio Neuquén Subgroup in the Neuquén Basin, Neuquen Province of Patagonia, Argentina. The holotype consists of an incomplete but well-preserved skeleton, lacking a skull, but including many vertebrae, the coracoids, a partial forelimb, pelvic girdle, and hindlimbs. Patagonykus has been classed with the Alvarezsauridae, a family which includes such taxa as the Mongolian Mononykus and the Argentinian Alvarezsaurus. In 2010 Gregory S. Paul estimated its length at 1 meter and its weight at 3.5 kg.
Rocasaurus is a genus of titanosaurian sauropod that lived in South America. Rocasaurus was discovered in Argentina in 2000, within the Allen Formation which is dated to be middle Campanian to early Maastrichtian in age. This genus grew up to 8 metres (26 ft) long, making it one of the smaller sauropods. It seems to be closely related to saltasaurid dinosaurs, like Saltasaurus and Neuquensaurus.
The Huincul Formation is a geologic formation of Late Cretaceous 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.
The Anacleto Formation is a geologic formation with outcrops in the Argentine Patagonian provinces of Mendoza, Río Negro, and Neuquén. It is the youngest formation within the Neuquén Group and belongs to the Río Colorado Subgroup. Formerly that subgroup was treated as a formation, and the Anacleto Formation was known as the Anacleto Member.
The La Colonia Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.
The Los Alamitos Formation is a geological formation of the North Patagonian Massif in Rio Negro Province, northwestern Patagonia, Argentina, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.
The Chorrillo Formation, also named as Chorillo Formation, is a Maastrichtian geologic formation in southern Patagonia, Argentina. The formation is more than 50 metres (160 ft) thick and underlies the Calafate Formation and rests on top of the La Irene Formation.
Bonapartenykus is a monospecific genus of alvarezsauroid dinosaur from Argentina that lived during the Late Cretaceous (Campanian-Maastrichtian) in what is now the upper Allen Formation of the Río Negro Province. The type and only species, Bonapartenykus ultimus, is known from a nearly articulated but partial skeleton that was found in close association to two incomplete eggs and several clusters of eggshells belonging to the oogenus Arriagadoolithus. Bonapartenykus was named in 2012 by Federico L. Agnolin, Jaime E. Powell, Fernando E. Novas and Martin Kundrát. Bonapartenykus has an estimated length of 2.5 m (8.2 ft) and weight of 72 kg (159 lb), making it the largest member of the clade Alvarezsauroidea.
Tralkasaurus is a genus of abelisaurid dinosaur from the Huincul Formation from Río Negro Province in Argentina. The type and only species is Tralkasaurus cuyi, named in 2020 by Mauricio Cerroni and colleagues based on an incomplete skeleton. A medium-sized abelisaurid, Tralkasaurus exhibits a conflicting blend of characteristics found among the early-diverging abelisauroids with others that characterize the highly specialized clade Brachyrostra, and thus its position within the clade is poorly-resolved.
Kaikaifilusaurus is an extinct genus of rhynchocephalians in the family Sphenodontidae from the Late Cretaceous of South America. Fossils of the genus were found in Cenomanian sediments of the Candeleros Formation and Turonian layers of the Huincul Formation, both of the Neuquén Basin and the Albian strata of the Cerro Barcino Formation in the Cañadón Asfalto Basin, all in Patagonia, Argentina. The genus contains two species, K. minimus and the type species K. calvoi.
Overoraptor is an extinct genus of paravian theropod of uncertain affinities from the Late Cretaceous Huincul Formation of Argentinian Patagonia. The genus contains a single species, O. chimentoi, known from several bones of the hands, feet, and hips alongside some vertebrae.
Niebla is a genus of abelisaurid theropod dinosaur from the Late Cretaceous Period (Campanian-Maastrichtian) of Río Negro province, Argentina. The genus contains a single species, Niebla antiqua, and is known from a partial, non-articulated skeleton. The holotype, found in the Allen Formation, represents an adult individual.
Meraxes is a genus of large carcharodontosaurid theropod dinosaur from the Late Cretaceous Huincul Formation of Patagonia, Argentina. The genus contains a single species, Meraxes gigas.
Patagopelta is an extinct genus of nodosaurine dinosaur from the Late Cretaceous Allen Formation of Argentina. The genus contains a single species, P. cristata, known from a partial skeleton. Patagopelta is a very small ankylosaur, comparable in size to the dwarf nodosaurid Struthiosaurus, about 2 m (6.6 ft) long.
Chucarosaurus is an extinct genus of titanosaurian dinosaur from the Late Cretaceous Huincul Formation of Argentina. The genus contains a single species, C. diripienda, known from various limb and pelvic bones.
Chakisaurus is an extinct genus of elasmarian ornithopod dinosaur from the Late Cretaceous Huincul Formation of Argentina. The genus contains a single species, C. nekul, known from multiple partial skeletons belonging to individuals of different ages. Chakisaurus represents the first ornithischian species to be named from the Huincul Formation.