Allen Formation

Allen Formation
Stratigraphic range: Mid Campanian-Maastrichtian ~73–66 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]

a study of pollen indicated the middle member of the Allen formation is late maastrichtian in age.^[6]

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Dinosaur eggs are known from the formation.^[7]

Ankylosaurs

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Ankylosauria[8]	Indeterminate	Arriagada Farm		Two teeth, five osteoderms, and a partial sacrum	Fossil remains possibly belonging to a parankylosaur distinct from Patagopelta
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[9]

Hadrosaurs

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	Cerro Matadero, Arriagada Farm	Upper	Partial skull, a cervical vertebrae, several sacrals, sternal rib and sternal plate, and multiple referred specimens found in a bonebed	A saurolophine hadrosaur[10]
Lapampasaurus	L. cholinoi	Islas Malvinas	Lower	Elements of the axial and appendicular skeleton of a subadult individual	A hadrosaur[11]
Willinakaqe	W. salitralensis	Salitral Moreno site.	Lower	A right premaxilla.	A saurolophine hadrosaur[12]

Sauropods

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Aeolosaurus	Indeterminate		Lower		A titanosaur[7]
Bonatitan	B.reigi[13]		Lower	Braincases, caudal vertebrae, and several limb elements	A titanosaur[13]
Menucocelsior	M. arriagadai		Lower	Seventeen caudal vertebrae and several appendicular bones: a right humerus, a left fibula and some metapodial.	A titanosaur[14]
Panamericansaurus	P. schroederi			"Five tail vertebrata, sacral vertebrae, left humerus and rib fragments"	A titanosaur[7][15]
Pellegrinisaurus?	P. powelli		Lower (if it is from the formation)	"Dorsal and caudal vertebrae, partial femur"	A titanosaur[7][15]
Rocasaurus	R. muniozi		Middle	"Partial postcranial skeleton"	A titanosaur[7][16]

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[17]
Limenavis	L. patagonica		Lower	"Partial forelimb"	An ornithuran[7][18]
Niebla	N. antiqua		Upper	Braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs, and incomplete vertebrae.	An abelisaurid[19]
Quilmesaurus	Q. curriei		Upper	Femur and distal tibia	An abelisaurid[7][20]

Fragmentary fossils are known from the formation.^[7]

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Aerotitan	A. sudamericanus	Bajo de Arriagada	Upper	Partial rostrum	The first unambiguous azhdarchid from South-America[21]

Genus[3]	Species	Location	Stratigraphic position	Material	Notes	Images
Atlantoceratodus	A. patagonicus			3 tooth plates	A ceratorontiform lungfish[22]
Belonostomus	B. lamarquensis				A aspidorhynchid fish[23]
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][24]	Species	Location	Stratigraphic position	Material	Notes	Images
Patagoniophis	P. parvus			incomplete trunk vertebra
Alamitophis	A. argentinus			incomplete trunk vertebra
Madtsoiidae	indeterminate			incomplete trunk vertebra
?Scincoidea	indeterminate			incomplete left maxilla
Pleurodonta	indeterminate			incomplete left maxilla
Teiioidea	indeterminate			incomplete right maxilla

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Iaremys	I. batrachomorpha				A chelid turtle[25]
Trapalcochelys	T. sulcata				A meiolaniform turtle[26]
Yaminuechelys	Y. gasperinii				A chelid turtle

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Lamarquesaurus	L. cabazai	Cerro Tortuga			[27]

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Kawanectes	K. lafquenianum	Quarry of the “Bentonitas Patagónicas” company	Upper	A partial skeleton consists of six cervical vertebrae, three dorsal vertebrae, three sacral vertebrae, nine caudal vertebrae, right femur, right humerus, ilium, one 216 mesopodial element, one caudal phalanx and one caudal rib .	An elasmosaur.

Unnamed frogs belonging to the family Calyptocephalellidae and Leptodactylidae, and those with no family designation were also found.^[28][3]

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Calyptocephalella	C. satan				Calyptocephalellid frog[29]
Kuruleufenia	K. xenopoides				Pipid frog[30]

The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species.^[31]

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.[32]
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.[33]		Fossil wood[33]

• 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". American Museum Novitates (3581): 1. doi:10.1206/0003-0082(2007)3581[1:ALCSMF]2.0.CO;2.
• Armas, Paula; Sánchez, María Lidia (30 January 2015). "Márgenes costeros híbridos de la Cuenca Neuquina (Formación Allen, Cretácico Superior, Argentina)". Andean Geology. 42 (1). Bibcode:2015AndGe..42a...6A. doi:10.5027/andgeoV42n1-a06.
• Coria, Rodolfo A.; Riga, Bernardo González; Casadío, Silvio (December 2012). "Un Nuevo Hadrosáurido (Dinosauria, Ornithopoda) de la Formación Allen, Provincia de la Pampa, Argentina". Ameghiniana. 49 (4): 552–572. Bibcode:2012Amegh..49..552C. doi:10.5710/AMGH.9.4.2012.487.
• Juárez Valieri, Rubén; Haro, José; Fiorelli, Lucas; Calvo, Jorge (2010). "A new hadrosauroid (Dinosauria: Ornithopoda) from the Allen Formation (Late Cretaceous) of Patagonia, Argentina". Revista del Museo Argentino de Ciencias Naturales. 12: 217–231. doi:10.22179/REVMACN.12.242. hdl:11336/147903.
• Novas, Fernando E.; Kundrat, Martin; Agnolín, Federico L.; Ezcurra, Martín D.; Ahlberg, Per Erik; Isasi, Marcelo P.; Arriagada, Alberto; Chafrat, Pablo (November 2012). "A new large pterosaur from the Late Cretaceous of Patagonia". Journal of Vertebrate Paleontology. 32 (6): 1447–1452. Bibcode:2012JVPal..32.1447N. doi:10.1080/02724634.2012.703979. hdl:11336/98097.
• Rougier, Guillermo W.; Chornogubsky, Laura; Casadio, Silvio; Arango, Natalia Paéz; Giallombardo, Andres (February 2009). "Mammals from the Allen Formation, Late Cretaceous, Argentina". Cretaceous Research. 30 (1): 223–238. Bibcode:2009CrRes..30..223R. doi:10.1016/j.cretres.2008.07.006. hdl:11336/103413.
• Salgado, Leonardo; Coria, Rodolfo A.; Magalhaes Ribeiro, Claudia M.; Garrido, Alberto; Rogers, Raymond; Simón, María E.; Arcucci, Andrea B.; Rogers, Kristina Curry; Carabajal, Ariana Paulina; Apesteguía, Sebastián; Fernández, Mariela; García, Rodolfo A.; Talevi, Marianella (June 2007). "Upper Cretaceous dinosaur nesting sites of Río Negro (Salitral Ojo de Agua and Salinas de Trapalcó-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.
• 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{{citation}}: CS1 maint: publisher location (link)

• O'gorman, José Patricio; Salgado, Leonardo; Gasparini, Zulma (March 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. Bibcode:2011Amegh..48..129O. doi:10.5710/AMGH.v48i1(308).