Allen Formation

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

Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Ankylosauria[7]	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[8]

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[9]
Lapampasaurus	L. cholinoi	Islas Malvinas	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

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]

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]

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]

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.^[27][3]

The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species.^[30]

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