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]
Uliana and Dellapé defined the formation's stratotype in 1981 in the eastern area of the Bajo de Añelo, where the relation between the base and top is clearly exposed. The deposits are mostly clastic, interbedded with banks of limestone and layers of anhydrite, which were defined as 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]
Armas and Sánchez performed a detailed facies analysis of the formation 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]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Dinosaur eggs are known from the formation. [6]
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Patagopelta | P. cristata | Salitral Moreno locality | Lower | Tooth, three posterior dorsal vertebrae, caudal vertebrae, two caudal centra, right femur, partial cervical half ring, and osteoderms. | A parankylosaur [7] |
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Bonapartesaurus | B. rionegrensis | Salitral Moreno and Islas Malvinas. | Lower | A partial skeleton. | A hadrosaur | |
Kelumapusaura | K. machi | Upper | Partial skull, a cervical vertebrae, several sacrals, sternal rib and sternal plate, and multiple referred specimens found in a bonebed | A saurolophine hadrosaur [8] | ||
Lapampasaurus | L. cholinoi | Lower | Elements of the axial and appendicular skeleton of a subadult individual | A hadrosaur [9] | ||
Willinakaqe | W. salitralensis | Salitral Moreno site. | Lower | A right premaxilla. | A saurolophine hadrosaur [10] | |
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Aeolosaurus | Indeterminate | Lower | A titanosaur [6] | |||
B.reigi [11] | Lower | Braincases, caudal vertebrae, and several limb elements | A titanosaur [11] | |||
Menucocelsior | M. arriagadai | Lower | Seventeen caudal vertebrae and several appendicular bones: a right humerus, a left fibula and some metapodial. | A titanosaur [12] | ||
Panamericansaurus | P. schroederi | "Five tail vertebrata, sacral vertebrae, left humerus and rib fragments" | A titanosaur [6] [13] | |||
Pellegrinisaurus? | P. powelli | Lower (if it is from the formation) | "Dorsal and caudal vertebrae, partial femur" | A titanosaur [6] [13] | ||
Rocasaurus | R. muniozi | Lower | "Partial postcranial skeleton" | A titanosaur [6] [14] | ||
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 | A holotype consists of a mid-dorsal vertebra, both scapulocoracoids, left tibia and femur, left pubis articulated with the pubic peduncle of the ilium, the anterior blade of the left ilium, and two partially preserved eggs. | An alvarezsauroid | ||
Lamarqueavis | L. australis | Lower | "Right coracoid with damaged sternal and omal extremities, and lacking acrocoracoidal process" | An ornithuran [15] | ||
Limenavis | L. patagonica | Lower | "Partial forelimb" | An ornithuran [6] [16] | ||
Niebla | N. antiqua | Upper | Braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs, and incomplete vertebrae. | An abelisaurid [17] | ||
Quilmesaurus | Q. curriei | Upper | Femur and distal tibia | An abelisaurid [6] [18] |
Fragmentary fossils are known from the formation. [6]
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Aerotitan | A. sudamericanus | Bajo de Arriagada | Upper | Partial rostrum | The first unambiguous azhdarchid from South-America [19] | |
Genus [3] | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Atlantoceratodus | A. patagonicus | 3 tooth plates | A ceratorontiform lungfish [20] | |||
Chondrichthyes | indeterminate | 11 vertebral centra | ||||
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 | ||||
Genus [3] | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Patagoniophis | P. parvus | incomplete trunk vertebra | ||||
Alamitophis | A. argentinus | incomplete trunk vertebra | ||||
Madtsoiidae | indeterminate | incomplete trunk vertebra | ||||
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Iaremys | I. batrachomorpha | A chelid turtle [21] | ||||
Yaminuechelys | Y. gasperinii | A chelid turtle | ||||
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Lamarquesaurus | L. cabazai | Cerro Tortuga | [22] | |||
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. [23] [3]
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Calyptocephalella | C. satan | Calyptocephalellid frog [24] | ||||
Kuruleufenia | K. xenopoides | Pipid frog [25] | ||||
The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species. [26]
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 | |
Solanutheirum | S. walshi | Cerro Tortuga | A right lower molar and left dentary fragment. | A meridiolestid. [27] | |
Trapalcotherium | T. matuastensis | Cerro Tortuga | One first lower molar | A gondwanathere | |
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
---|---|---|---|---|---|---|
Podocarpoxylon | P. mazzonii | Valcheta Petrified Forest, Río Negro Province. [28] | Fossil wood [28] | |||
Abelisauridae is a family of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indian subcontinent and the island of Madagascar. Isolated teeth were found in the Late Jurassic of Portugal, and the Late Cretaceous genera Tarascosaurus, Arcovenator and Caletodraco have been described in France. Abelisaurids possibly first appeared during the Jurassic period based on fossil records, and some genera survived until the end of the Mesozoic era, around 66 million years ago.
Bonitasaura is a genus of 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 a lower jaw with teeth, a partial vertebrae series, and limb bones, were described by Sebastian Apesteguía in 2004.
Megaraptor is a genus of large theropod dinosaur that lived in the ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Initially thought to have been a giant dromaeosaur-like coelurosaur, it was classified as a neovenatorid allosauroid in previous phylogenies, but more recent phylogeny and discoveries of related megaraptoran genera has placed it as either a basal tyrannosauroid or a basal coelurosaur with some studies still considering it a neovenatorid.
Notohypsilophodon is a genus of ornithopod dinosaur from the Late Cretaceous of Argentina. It was described as the only "hypsilophodont" known from South America, although this assessment is not universally supported, and Gasparinisaura is now believed to have been a basal euornithopod as well.
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 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.
Taurovenator is a large carcharodontosaurid theropod from the late Cretaceous Huincul Formation of Argentina that lived during the Cenomanian age of the Late Cretaceous. It is monotypic, containing only one species, T. violantei.
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.
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 about nine years old in minimum age.
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 ankylosaurian dinosaur from the Late Cretaceous Allen Formation of Argentina. The genus contains a single species, P. cristata, known from a partial skeleton. While originally described as a nodosaurine, later discoveries provided support for parankylosaurian affinities for the taxon. Patagopelta is a very small ankylosaur, comparable in size to the dwarf nodosaurid Struthiosaurus, about 2 m (6.6 ft) long.
Yatenavis is an extinct genus of enantiornithine bird from the Late Cretaceous Chorrillo Formation of Santa Cruz Province, Argentina. The genus contains a single species, Y. ieujensis, known from a partial humerus.
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.
Sidersaura is an extinct genus of rebbachisaurid sauropod dinosaur from the Late Cretaceous Huincul Formation of Argentina. The genus contains a single species, S. marae, known from the remains of four individuals. Sidersaura represents one of the largest known rebbachisaurids.
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.
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