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]
Fauna of 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]
Life restoration of Dinosaurs discovered from Allen Formation
Color key
Notes Uncertain or tentative taxa are in small text ; crossed out taxa are discredited.
Dinosaur eggs are known from the formation.[ 6]
Ankylosaurs
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 [ 7]
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
Upper
Partial skull, a cervical vertebrae, several sacrals, sternal rib and sternal plate, and multiple referred specimens found in a bonebed
A saurolophine hadrosaur[ 8]
Lapampasaurus
L. cholinoi
Lower
Elements of the axial and appendicular skeleton of a subadult individual
A hadrosaur[ 9]
Willinakaqe
W. salitralensis
Salitral Moreno site.
Lower
A right premaxilla.
A saurolophine hadrosaur[ 10]
Sauropods
Genus
Species
Location
Stratigraphic position
Material
Notes
Images
Aeolosaurus
Indeterminate
Lower
A titanosaur [ 6]
Bonatitan
B.reigi [ 11]
Lower
Braincases, caudal vertebrae, and several limb elements
A titanosaur[ 11]
Menucocelsior
M. arriagadai
Lower
Seventeen caudal vertebrae and several appendicular bones: a right humerus, a left fibula and some metapodial.
A titanosaur
Panamericansaurus
P. schroederi
"Five tail vertebrata, sacral vertebrae, left humerus and rib fragments"
A titanosaur[ 6] [ 13]
Pellegrinisaurus ?
P. powelli
Lower (if it is from the formation)
"Dorsal and caudal vertebrae, partial femur"
A titanosaur[ 6] [ 13]
Rocasaurus
R. muniozi
Lower
"Partial postcranial skeleton"
A titanosaur[ 6] [ 14]
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 [ 15]
Limenavis
L. patagonica
Lower
"Partial forelimb"
An ornithuran[ 6] [ 16]
Niebla
N. antiqua
Upper
Braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs, and incomplete vertebrae.
An abelisaurid[ 17]
Quilmesaurus
Q. curriei
Upper
Femur and distal tibia
An abelisaurid[ 6] [ 18]
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[ 19]
Genus[ 3]
Species
Location
Stratigraphic position
Material
Notes
Images
Patagoniophis
P. parvus
incomplete trunk vertebra
Alamitophis
A. argentinus
incomplete trunk vertebra
Madtsoiidae
indeterminate
incomplete trunk vertebra
Genus
Species
Location
Stratigraphic position
Material
Notes
Images
Lamarquesaurus
L. cabazai
Cerro Tortuga
[ 22]
Genus
Species
Location
Stratigraphic position
Material
Notes
Images
Kawanectes
K. lafquenianum
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]
^ Salgado et al., 2007
^ 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 .
^ a b c d Martinelli, A. and Forasiepi, A.M. (2004). "Late Cretaceous vertebrates from Bajo de Santa Rosa (Allen Formation), Rio Negro province, Argentina, with the description of a new sauropod dinosaur (Titanosauridae)". Revista del Museo Argentino de Ciencias Naturales 6(2): 257–305.
^ a b Armas & Sánchez, 2015, p.101
^ Armas & Sánchez, 2015, p.110
^ a b c d e f g h Weishampel et al., 2004, p.604
^ Soto Acuña, Sergio; Vargas, Alexander O.; Kaluza, Jonatan (2024). "A new look at the first dinosaur discovered in Antarctica: reappraisal of Antarctopelta oliveroi (Ankylosauria: Parankylosauria)" . Advances in Polar Science . 35 (1): 78–107. doi :10.12429/j.advps.2023.0036 .
^ Rozadilla, S.; Brissón-Egli, F.; Agnolín, F.L.; Aranciaga-Rolando, A.M.; Novas, F.E. (2022). "A new hadrosaurid (Dinosauria: Ornithischia) from the Late Cretaceous of northern Patagonia and the radiation of South American hadrosaurids". Journal of Systematic Palaeontology . 19 (17): 1207–1235. doi :10.1080/14772019.2021.2020917 . S2CID 247122005 .
^ Coria et al., 2012
^ Juárez Valieri et al., 2010
^ a b "63.10 Provincia de Río Negro, Argentina; 4. Río Colorado Formation," in Weishampel, et al. (2004). Page 604.
^ a b "Table 13.1," in Weishampel, et al., 2004, p.269
^ "Table 13.1," in Weishampel, et al., 2004, p.270
^ Agnolin, 2010
^ "Table 11.1," in Weishampel, et al., 2004, p.215
^ 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 . 105 : 102915. doi :10.1016/j.jsames.2020.102915 . hdl :11336/150468 . ISSN 0895-9811 . S2CID 225123133 .
^ "Table 4.1," in Weishampel, et al., 2004, p.77
^ Novas et al., 2012
^ Federico Agnolin (2010). "A new species of the genus Atlantoceratodus (Dipnoiformes: Ceratodontoidei) from the Uppermost Cretaceous of Patagonia and a brief overview of fossil dipnoans from the Cretaceous and Paleogene of South America" . Brazilian Geographical Journal: Geosciences and Humanities Research Medium . 1 (2): 162–210.
^ Agnolín, F. L.; Aranciaga-Rolando, A. M.; Ortiz, R. (2024). "New chelid turtle with a flattened skull from the Late Cretaceous of Northern Patagonia, Argentina". Alcheringa: An Australasian Journal of Palaeontology . doi :10.1080/03115518.2024.2427261 .
^ Apesteguía & Rougier, 2007, p.3
^ Suazo Lara, F.; Gómez, R. O. (2022-03-01). "In the shadow of dinosaurs: Late Cretaceous frogs are distinct components of a widespread tetrapod assemblage across Argentinean and Chilean Patagonia" . Cretaceous Research . 131 : 105085. Bibcode :2022CrRes.13105085S . doi :10.1016/j.cretres.2021.105085 . ISSN 0195-6671 . S2CID 243482426 .
^ Federico Agnolin (2012). "A new Calyptocephalellidae (Anura, Neobatrachia) from the Upper Cretaceous of Patagonia, Argentina, with comments on its systematic position" . Studia Geologica Salmanticensia . 48 (2): 129–178.
^ Gómez, Raúl O. (2016-07-01). "A new pipid frog from the Upper Cretaceous of Patagonia and early evolution of crown-group Pipidae" . Cretaceous Research . 62 : 52–64. Bibcode :2016CrRes..62...52G . doi :10.1016/j.cretres.2016.02.006 . hdl :11336/59544 . ISSN 0195-6671 .
^ Rougier et al., 2009
^ Connelly, B. E.; Cardozo, M. S.; Montgomery, J. D.; Rougier, G. W. (2024). "New mammals from the Upper Cretaceous Allen Formation (Patagonia, Argentina) and reassessment of meridiolestidan diversity". Cretaceous Research . 162 . 105935. doi :10.1016/j.cretres.2024.105935 .
^ a b Passalia, M. G.; Garrido, A.; Iglesias, A.; Vera, E. I. (2022-10-14). "The Valcheta Petrified Forest (Upper Cretaceous), Northern Patagonia, Argentina: A Geological And Paleobotanical Survey" . Cretaceous Research . 142 : 105395. doi :10.1016/j.cretres.2022.105395 . ISSN 0195-6671 . S2CID 252964524 .
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: CS1 maint: multiple names: authors list (link )
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