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
~73–69 Ma
↓
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
Coordinates40.0°S 66.6°W / -40.0; -66.6
Approximate paleocoordinates42.8°S 52.2°W / -42.8; -52.2
RegionNeuquén, Río Negro & La Pampa Provinces
Country Argentina
ExtentNeuquén Basin
Type section
Named byUliana & Dellapé
Year defined1981
Allen Formation (Argentina)

Description
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 Lower
[5]
Austroraptor A. cabazai
Bonapartesaurus B. rionegrensis Lower
Bonapartenykus B. ultimus Lower

Bonatitan[6]

B.reigi[6]

 Lower
Lamarqueavis L. australis "Right coracoid with damaged sternal and omal extremities, and lacking acrocoracoidal process"
[7]
Lapampasaurus L. cholinoi Elements of the axial and appendicular skeleton of a subadult individual
[8]
Laplatasaurus L. araukanicus
[5]
Limenavis L. patagonica Lower "Partial forelimb"
[5][9]
Niebla N. antiqua Braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs, and incomplete vertebrae. [10]
Nodosauridae Indeterminate Lower Tooth, three posterior dorsal vertebrae, caudal vertebrae, two caudal centra, right femur, partial cervical half ring, and osteoderms. [11]
Panamericansaurus P. schroederi "Five tail vertebrata, sacral vertebrae, left humerus and rib fragments"
[5][12]
Pellegrinisaurus P. powelli "Dorsal and caudal vertebrae, partial femur"
[5][12]
Quilmesaurus Q. curriei Femur and distal tibia
[5][13]
Rocasaurus R. muniozi Lower "Partial postcranial skeleton"
[5][14]
Willinakaqe W. salitralensis Lower
[15]

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[16]

Rhynchocephalia
SpeciesLocationNotesImages
Rhynchocephalia from the Allen Formation
Lamarquesaurus cabazaiCerro Tortuga[17]

Plesiosauria
SpeciesLocationNotesImages
Plesiosauria from the Allen Formation
Kawanectes lafquenianum

Mammals

The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species.[18]

Mammals reported from the Allen Formation
GenusSpeciesLocationMaterialNotesImages
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. Armas & Sánchez, 2015, p.101
  4. Armas & Sánchez, 2015, p.110
  5. Weishampel et al., 2004, p.604
  6. "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. Aranciaga Rolando, Mauro; Cerroni, Mauricio A.; Garcia Marsà, Jordi A.; Agnolín, Federico l.; Motta, Matías J.; Rozadilla, Sebastián; Brisson Eglí, Federico; Novas, Fernando E. (2020-10-14). "A new medium-sized abelisaurid (Theropoda, Dinosauria) from the late cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina". Journal of South American Earth Sciences: 102915. doi:10.1016/j.jsames.2020.102915. ISSN 0895-9811.
  11. Arbour, Victoria M.; Currie, Philip J. (2016-05-03). "Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs". Journal of Systematic Palaeontology. 14 (5): 385–444. doi:10.1080/14772019.2015.1059985. ISSN 1477-2019.
  12. "Table 13.1," in Weishampel, et al., 2004, p.269
  13. "Table 4.1," in Weishampel, et al., 2004, p.77
  14. "Table 13.1," in Weishampel, et al., 2004, p.270
  15. Juárez Valieri et al., 2010
  16. Novas et al., 2012
  17. Apesteguía & Rougier, 2007, p.3
  18. Rougier et al., 2009

Bibliography

Further reading
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.