Allen Formation

Allen Formation
Stratigraphic range: Mid Campanian-Maastrichtian ~73–69 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Outcrop of the Allen and Anacleto Formations at Auca Mahuida
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′S 66°36′W / 40.0°S 66.6°W / -40.0; -66.6
Approximate paleocoordinates	42°48′S 52°12′W / 42.8°S 52.2°W / -42.8; -52.2
Region	Neuquén, Río Negro & La Pampa Provinces
Country	Argentina
Extent	Neuquén Basin
Type section
Named by	Uliana & Dellapé
Year defined	1981
Allen Formation (Argentina)

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]

Dinosaur eggs are known from the formation.^[6]

Ankylosaurs

Ankylosaurs reported from the Allen Formation
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 of uncertain affinities. [7][8]

Hadrosaurs

Hadrosaurs reported from the Allen Formation
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. [9]
Lapampasaurus	L. cholinoi		Lower	Elements of the axial and appendicular skeleton of a subadult individual	A hadrosaur. [10]
Willinakaqe	W. salitralensis	Salitral Moreno site.	Lower	A right premaxilla.	A saurolophine hadrosaur. [11]

Sauropods

Sauropods reported from the Allen Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Aeolosaurus	Indeterminate		Lower		A titanosaur. [6]
Bonatitan	B.reigi[12]		Lower	Braincases, caudal vertebrae, and several limb elements	A titanosaur. [12]
Menucocelsior	M. arriagadai		Lower	Seventeen caudal vertebrae and several appendicular bones: a right humerus, a left fibula and some metapodial.	A titanosaur. [13]
Panamericansaurus	P. schroederi			"Five tail vertebrata, sacral vertebrae, left humerus and rib fragments"	A titanosaur. [6][14]
Pellegrinisaurus?	P. powelli		Lower (if it is from the formation)	"Dorsal and caudal vertebrae, partial femur"	A titanosaur. [6][14]
Rocasaurus	R. muniozi		Lower	"Partial postcranial skeleton"	A titanosaur. [6][15]

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	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. [16]
Limenavis	L. patagonica		Lower	"Partial forelimb"	An ornithuran. [6][17]
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. [6][19]

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	Upper	Partial rostrum	The first unambiguous azhdarchid from South-America[20]

Unnamed frogs belonging to the family Calyptocephalellidae and Leptodactylidae, and those with no family designation were also found.^[23][3]

The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species.^[26]

• List of dinosaur-bearing rock formations
• Adamantina Formation
• La Colonia Formation
• Lecho Formation
• Los Alamitos Formation
• Los Llanos Formation
• Marília Formation

• Agnolin, Federico L (2010), "An avian coracoid from the Upper Cretaceous of Patagonia, Argentina", Studia Geologica Salmanticensia, 46 (2): 99–119, retrieved 2019-02-16
• Apesteguía, Sebastián; Rougier, Guillermo W. (2007), "A Late Campanian Sphenodontid Maxilla from Northern Patagonia" (PDF), American Museum Novitates (3581): 1–12, doi:10.1206/0003-0082(2007)3581[1:ALCSMF]2.0.CO;2, retrieved 2019-03-30
• Armas, Paula; Sánchez, María Lidia (2015), "Hybrid coastal edges in the Neuquén Basin (Allen Formation, Upper Cretaceous, Argentina)" (PDF), Andean Geology, 42: 97–113, retrieved 2018-10-02
• Coria, Rodolfo A.; González Riga, Bernardo; Casadío, Silvio (2012), "Un nuevo hadrosáurido (Dinosauria, Ornithopoda) de la Formación Allen, provincia de La Pampa, Argentina", Ameghiniana, 49 (4): 552–572, doi:10.5710/AMGH.9.4.2012.487, retrieved 2019-02-16
• Juárez Valieri, Rubén D.; Haro, José A.; Fiorelli, Lucas E.; Calvo, Jorge O. (2010), "A new hadrosauroid (Dinosauria: Ornithopoda) from the Allen Formation (Late Cretaceous) of Patagonia, Argentina", Revista del Museo Argentino de Ciencias Naturales, New Series, 11 (2): 217–231, doi:10.22179/REVMACN.12.242, hdl:11336/147903, retrieved 2019-02-16
• Novas, F.E.; Kundrat, M.; Agnolín, F.L.; Ezcurra, M.N.D.; Ahlberg, P.E.; Isasi, M.P.; Arriagada, A.; Chafrat, P. (2012), "A new large pterosaur from the Late Cretaceous of Patagonia" (PDF), Journal of Vertebrate Paleontology, 32 (6): 1447, Bibcode:2012JVPal..32.1447N, doi:10.1080/02724634.2012.703979, hdl:11336/98097, retrieved 2019-02-16
• Rougier, G.W.; Chornogubsky, L.; Casadio, S.; Paéz Arango, N.; Giallombardo, A. (2009), "Mammals from the Allen Formation, Late Cretaceous, Argentina (subscription required)", Cretaceous Research, 30 (1): 223–238, Bibcode:2009CrRes..30..223R, doi:10.1016/j.cretres.2008.07.006, hdl:11336/103413, retrieved 2019-02-16
• Salgado, L.; Coria, R.A.; Magalheas Ribeiro, C.M.; Garrido, A.; Rogers, R.; Simon, M.E.; Arcucci, A.B.; Rogers, Carabajal, A. P., Apesteguia, S., Fernandez, M., Garcia, R. A., and Talevi, M., K.C. (2007), "Upper Cretaceous dinosaur nesting sites of Rio Negro (Salitral Ojo de Agua and Salinas de Trapalco-Salitral de Santa Rosa), northern Patagonia, Argentina", Cretaceous Research, 28 (3): 392–404, Bibcode:2007CrRes..28..392S, doi:10.1016/j.cretres.2006.06.007, hdl:11336/183909, retrieved 2019-02-16{{citation}}: CS1 maint: multiple names: authors list (link)
• Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (2004), The Dinosauria, 2nd edition, Berkeley: University of California Press, pp. 1–880, ISBN 0-520-24209-2, retrieved 2019-02-21

Wikimedia Commons has media related to Allen Formation.

• O'Gorman, J. P., Salgado, L., y Gasparini, Z., 2011. Plesiosaurios de la Formación Allen (Campaniano-Maastrichtiano) en el área del Salitral de Santa Rosa (Provincia de Río Negro, Argentina). Ameghiniana 48 (1): 129-135