Allen Formation

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]

Allen Formation
Stratigraphic range: Mid Campanian-Maastrichtian
~79–69 Ma
Fms Anacleto Allen Auca Mahuida 1
Outcrop of the Allen and Anacleto Formations at Auca Mahuida
TypeGeological formation
Unit ofMalargüe Group
UnderliesJagüel Formation
OverliesAnacleto Formation
Thicknessup to 70 m (230 ft)
Lithology
PrimaryMudstone, sandstone
OtherLimestone
Location
Coordinates40°00′S 66°36′W / 40.0°S 66.6°WCoordinates: 40°00′S 66°36′W / 40.0°S 66.6°W
Approximate paleocoordinates42°48′S 52°12′W / 42.8°S 52.2°W
RegionNeuquén, Río Negro & La Pampa Provinces
Country Argentina
ExtentNeuquén Basin
Type section
Named byUliana & Dellapé
Year defined1981
Allen Formation is located in Argentina
Allen Formation
Allen Formation (Argentina)

Description

Allen Formation Fauna
Fauna of Allen

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.[3]

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.[3]

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.[4]

Fossil content

Dinosaurs

Dinosaur eggs are known from the formation.[5]

Dinosaurs reported from the Allen Formation
Genus Species Location Stratigraphic position Material Notes Images
Aeolosaurus Indeterminate
Aeolosaurus copia
Austroraptor A. cabazai
Austroraptor Reconstruction

Bonatitan[6]

B.reigi[6]

Lamarqueavis L. australis "Right coracoid with damaged sternal and omal extremities, and lacking acrocoracoidal process"
Lapampasaurus L. cholinoi Elements of the axial and appendicular skeleton of a subadult individual
Laplatasaurus L. araukanicus
Limenavis L. patagonica "Partial forelimb"
Panamericansaurus P. schroederi "Five tail vertebrata, sacral vertebrae, left humerus and rib fragments"
Pellegrinisaurus P. powelli "Dorsal and caudal vertebrae, partial femur"
Quilmesaurus Q. curriei Femur and distal tibia
Quilmesaurus curriei
Rocasaurus R. muniozi "Partial postcranial skeleton"
Saltasaurus S. loricatus
Saltasaurus dinosaur

Saltasaurus loricatus egg
Willinakaqe W. salitralensis
Bonapartesaurus

Pterosaurs

Fragmentary fossils are known from the formation.[5]

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[14]
Aerotitan

Rhynchocephalia

Species Location Notes Images
Rhynchocephalia from the Allen Formation
Lamarquesaurus cabazai Cerro Tortuga [15]

Mammals

The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species.[16]

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

See also

References

  1. ^ Salgado et al., 2007
  2. ^ Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, South America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 600-604. ISBN 0-520-24209-2.
  3. ^ a b Armas & Sánchez, 2015, p.101
  4. ^ Armas & Sánchez, 2015, p.110
  5. ^ a b c d e f g h i j Weishampel et al., 2004, p.604
  6. ^ a b c "63.10 Provincia de Río Negro, Argentina; 4. Río Colorado Formation," in Weishampel, et al. (2004). Page 604.
  7. ^ Agnolin, 2010
  8. ^ Coria et al., 2012
  9. ^ "Table 11.1," in Weishampel, et al., 2004, p.215
  10. ^ a b "Table 13.1," in Weishampel, et al., 2004, p.269
  11. ^ "Table 4.1," in Weishampel, et al., 2004, p.77
  12. ^ "Table 13.1," in Weishampel, et al., 2004, p.270
  13. ^ Juárez Valieri et al., 2010
  14. ^ Novas et al., 2012
  15. ^ Apesteguía & Rougier, 2007, p.3
  16. ^ Rougier et al., 2009

Bibliography

Further reading

Aeolosaurus

Aeolosaurus (; "Aeolus' lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America. Like most sauropods, it would have been a quadrupedal herbivore with a long neck and tail. Aeolosaurus is well known for a titanosaur, as it is represented by the remains of several individuals belonging to at least three species. However, like most titanosaurs, no remains of the skull are known.

The holotype of Aeolosaurus rionegrinus consists of a series of seven tail vertebrae, as well as parts of both forelimbs and the right hindlimb. It was discovered in the Angostura Colorada Formation in Argentina, which dates from the Campanian stage of the Late Cretaceous, about 83 to 74 million years ago.

Aerotitan

Aerotitan is a genus of large azhdarchid pterosaur known from the Late Cretaceous Allen Formation of the Neuquén Basin in northern Patagonia, Argentina.

Austroraptor

Austroraptor ( AW-stroh-RAP-tər) is an extinct genus of dromaeosaurid dinosaur that lived about 70 million years ago during the Cretaceous Period in what is now modern Argentina. Austroraptor was a medium sized, moderately-built, ground-dwelling, bipedal carnivore, that could grow up to 5–6 m (16.4–19.7 ft) long. Its length makes Austroraptor one of the largest dromaeosaurids known, with only Achillobator, Dakotaraptor, and Utahraptor approaching or surpassing it in length. It is the largest dromaeosaur to be discovered in the Southern Hemisphere. Particularly notable about the taxon were its relatively short forearms, much shorter in proportion when compared to the majority of the members of its group.

Bonapartenykus

Bonapartenykus (named in honor of José Bonaparte) is a genus of alvarezsaurid theropod dinosaurs known from the Late Cretaceous (Campanian/Maastrichtian stage) Allen Formation of northwestern Patagonia, Argentina. The type species is B. ultimus. An adult female of B. ultimus has been discovered with two eggs that may have still been inside its oviducts, although some evidence suggests that the eggs may have been incubated in a nest. The size of the adult female has been estimated as at least 8.5 feet (2.6 m), and the weight of Bonapartenykus has been estimated as 100 pounds (45 kg). Its diet probably consisted of insects. Paleontologist Fernando Novas compared its bones to those of the ñandú, a modern-day Patagonian flightless bird.The eggs of Bonapartenykus were considered unique enough for them to be given a new parataxonomic name, Arriagadoolithus, which was classified in a new oofamily, the Arriagadoolithidae, so named for the owner of the site where the discovery was made.

Bonapartesaurus

Bonapartesaurus is an extinct genus of herbivorous ornithopod dinosaur belonging to Hadrosauridae, which lived in the area of the modern Argentina during the Campanian and Maastrichtian stages of the Late Cretaceous.

Bonatitan

Bonatitan is a genus of titanosaurian dinosaur from the Late Cretaceous Allen Formation of Argentina.

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. Campanian spans the time from 83.6 (± 0.7) to 72.1 (± 0.6) million years ago. It is preceded by the Santonian and it is followed by the Maastrichtian.The Campanian was an age when a worldwide sea level rise covered many coastal areas. The morphology of some of these areas has been preserved: it is an unconformity beneath a cover of marine sedimentary rocks.

Kawanectes

Kawanectes (meaning "Kawas swimmer") is a genus of elasmosaurid plesiosaur, a type of long-necked marine reptile, that lived in the oceans of Late Cretaceous Patagonia. It contains one species, K. lafquenianum, described in 2016 by O'Gorman.

Lapampasaurus

Lapampasaurus is an extinct genus of hadrosaurid known from the Late Cretaceous Allen Formation (late Campanian or early Maastrichtian stage) of La Pampa Province, Argentina. It contains a single species, Lapampasaurus cholinoi.The generic name refers to the Argentine province of La Pampa. The specific name honours the late collector José Cholino. The material includes cervical, dorsal, sacral and caudal vertebrae, the forelimb girdle, and the partial hindlimb.

Laplatasaurus

Laplatasaurus (meaning "La Plata lizard", named for La Plata, Argentina) is a genus of titanosaurian sauropod dinosaur that lived during the Late Cretaceous in South America.

The genus was named in 1927 by Friedrich von Huene, but without a description, so that it remained a nomen nudum. In 1929 the type species, Laplatasaurus araukanicus, was described by Huene. The generic name refers to La Plata. The specific name is derived from the Araucanos or Mapuche. By accident Huene in 1929 also mentioned a "Laplatasaurus wichmannianus" but that was a lapsus calami for Antarctosaurus wichmannianus. In 1933 however, he and Charles Alfred Matley renamed Titanosaurus madagascariensis to Laplatasaurus madagascariensis. This last species is today commonly referred to the original Titanosaurus.

Huene based Laplatasaurus on fragmentary material found in three locations in Argentina, in strata of the Allen Formation, dating from the Campanian faunal stage. It consisted of limb elements, some dorsal vertebrae and a series of caudal vertebrae. Part of the finds had earlier been referred by Richard Lydekker to Titanosaurus australis. Huene never assigned a holotype, but in 1979 José Fernando Bonaparte chose MLP 26-306 as the lectotype, a specimen consisting of a tibia and a fibula that perhaps originate from different individuals.

Huene assigned those fossils to Laplatasaurus that seemed to indicate a rather large yet at the same time elegantly built sauropod. The about eighteen metres (60 ft) long Laplatasaurus was perhaps similar to Saltasaurus. Osteoderms forming an armored plating on the back, have been referred to Laplatasaurus but the association is uncertain. These plates had much smaller ridges than those of Saltasaurus.

Huene placed Laplatasaurus in the Titanosauridae, which is still a common classification. In his 2003 review of South American titanosaurs, Jaime Eduardo Powell assigned Laplatasaurus to Titanosaurus, creating the new combination Titanosaurus aurakanicus. Others however, continued to treat Laplatasaurus as valid genus separate from Titanosaurus.A 2015 re-assessment of Laplatasaurus found it to be closely related to Bonitasaura, Futalognkosaurus, Mendozasaurus, and Uberabatitan. The genus was restricted to the lectotype, and the material from Rancho de Avila was assigned to cf. Bonitasaura sp.

Loricosaurus

Loricosaurus (meaning "armour lizard") is a genus of sauropod represented by a single species. It is a titanosaurian that lived near the end of the Late Cretaceous period, approximately 71 million years ago in the late Campanian or early Maastrichtian. Found in the province of Neuquen, Argentina in the Allen Formation. Due to the presence of armour, at first it was thought that it was an ankylosaur, but today it is considered to be the armour of a titanosaur.

Panamericansaurus

Panamericansaurus is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America. It is very similar to the closely related Aeolosaurus, differing only in details of the vertebrae.

The type species Panamericansaurus schroederi was named and described by Jorge Orlando Calvo and Juan Domingo Porfiri in 2010. The generic name refers to the Pan American Energy company which financially supported the paleontological investigations. The specific name honours the Schroeder family on whose land the remains were found. The describers placed Panamericansaurus in a clade within the Titanosauridae, the Aeolosaurini, of which also Aeolosaurus and Gondwanatitan are members.

The holotype MUCPv-417 was in June 2003 found near San Patricio del Chañar, in Neuquén in a layer of the Allen Formation dating from the Campanian-Maastrichtian. It consists of five tail vertebrae, a sacral vertebra, a left humerus, haemal arches and rib fragments. The humerus is 123 centimetres long. The total length of the holotype individual was estimated at eleven metres.

Pellegrinisaurus

Pellegrinisaurus (meaning "Lizard from Pelligrini") is the name given to a genus of dinosaur from the Late Cretaceous. It was a titanosaur which lived in what is now Argentina, found in the Anacleto and Allen Formations, stretching the range of Pellegrinisaurus from early to late Campanian in age. The type species, Pellegrinisaurus powelli, was described by Salgado in 1996, and is based on mostly vertebrae. Pelligrinisaurus is estimated to have been between 62 and 78 feet (19 and 24 m) in length, but because a full fossil skeleton has not been recovered, this is only a rough estimate.

Quilmesaurus

Quilmesaurus is a genus of carnivorous theropod dinosaur from the Patagonian Upper Cretaceous (Campanian stage) 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 (more commonly known as a nomen dubium, or "dubious name").

Rocasaurus

Rocasaurus (meaning "Roca lizard") 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 (75 to 70 million years ago in the Late Cretaceous). 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 type species, Rocasaurus muniozi, was formally described by Leonardo Salgado and Azpilicueta in 2000.

Saltasaurus

Saltasaurus (which means "lizard from Salta") is a genus of titanosaurid sauropod dinosaur of the Late Cretaceous Period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, Saltasaurus was characterized by a short neck and stubby limbs. It was the first genus of sauropod known to possess armour of bony plates embedded in its skin. Such small bony plates, called osteoderms, have since been found on other titanosaurids.

Trapalcotherium

Trapalcotherium is a fossil mammal from the Cretaceous of Argentina in the family Ferugliotheriidae. The single species, T. matuastensis, is known from one tooth, a first lower molar. It is from the Allen Formation, which is probably Maastrichtian in age, and was first described in 2009. The tooth bears two rows of cusps, one at the inner (lingual) side and the other at the outer (labial) side, which are connected by transverse ridges separated by deep valleys. This pattern is reminiscent of Ferugliotherium, a gondwanathere mammal from similarly aged deposits in Argentina, and Trapalcotherium is therefore recognized as a member of the same family Ferugliotheriidae. Ferugliotheriidae is one of two families of gondwanatheres, an enigmatic group without close relationships to any living mammals.

Willinakaqe

Willinakaqe is a possibly invalid genus of saurolophine hadrosaurid dinosaur described based on fossils the late Cretaceous (late Campanian-early Maastrichtian stage) of the Río Negro Province of southern Argentina.

Yaminuechelys

Yaminuechelys is an extinct genus of chelid turtle from Argentina. The genus first appeared during the Late Cretaceous, and then becomes extinct during the Late Paleocene.

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