Bajo de la Carpa Formation

Geological formation in Argentina

Bajo de la Carpa Formation
Stratigraphic range: Mid-Late Santonian ~86–83 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Juan D. Porfiri excavating the holotype of Diuqin lechiguanae from the Bajo de la Carpa Formation
Type	Geological formation
Unit of	Neuquén Group Río Colorado Subgroup
Underlies	Anacleto Formation
Overlies	Río Neuquén Subgroup Plottier Formation
Thickness	Up to 150 m (490 ft)
Lithology
Primary	Sandstone
Other	Mudstone, siltstone, paleosol
Location
Coordinates	Bajo de la Carpa Formation (Argentina)

The Bajo de la Carpa Formation is a geologic formation of the Neuquén Basin that crops out in northern Patagonia, in the provinces of Río Negro and Neuquén, Argentina. It is the oldest of two formations belonging to the Río Colorado Subgroup within the Neuquén Group. Formerly, that subgroup was treated as a formation, and the Bajo de la Carpa Formation was known as the Bajo de la Carpa Member.^[1]

At its base, this formation conformably overlies the Plottier Formation of the older Río Neuquén Subgroup, and it is in turn overlain by the Anacleto Formation, the youngest and uppermost formation of the Neuquén Group.^[2]^[3]

The Bajo de la Carpa Formation can reach 150 metres (490 ft) in thickness in some locations, and consists mainly of sandstones of various colors, all of fluvial origin, with thin layers of mudstone and siltstone in between. Geological features such as geodes, chemical nodules, impressions of raindrops, and paleosols (fossil soils) are commonly found in this formation as well.^[1]^[3]

Fossil content

Reptiles

Vertebrate fossils are abundant within the Bajo de la Carpa Formation:

a snake-necked turtle, Lomalatachelys
a lizard, Paleochelco
the snake Dinilysia
diverse crocodylomorphs occupying a range of ecological niches: Comahuesuchus, Cynodontosuchus, Lomasuchus, Gasparinisuchus,^[4] Neuquensuchus universitas,^[5] Notosuchus, Peirosaurus, Kinesuchus overoi,^[6] and Barrosasuchus neuquenianus^[7]

Small nests with eggs inside, found in this formation, probably belonged to the bird Neuquenornis.^[3] Fossil wasp nests have also been found in these rocks.^[1]^[3]

Dinosaurs

Ornithischians

Ornithischians reported from the Allen Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Ankylosauria^[8]	Indetermidate.
Mahuidacursor^[9]	M. lipanglef				An ornithopod.

Sauropods

Sauropods reported from the Allen Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Bonitasaura	B. salgadoi				A titanosaur.
Inawentu	I. oslatus				A titanosaur.
Overosaurus	O. paradasorum				A titanosaur.
Rinconsaurus	R. caudamirus				A titanosaur.
Traukutitan^[10]	T. eocaudata				A titanosaur.

Theropods

Theropods reported from the Allen Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Achillesaurus	A. manazzonei		Upper	A partial skeleton consists of a sacral vertebra, four tail vertebrae, part of the left thighbone, shin, and foot, and the left ilium.	An alvarezsaurid.
Alvarezsaurus	A. calvoi				An alvarezsaurid.
Diuqin^[11]	D. lechiguanae	"the isthmus between the southeast coast of Lago Barreales and the northwest coast of Lago Mari Menuco"		A fragmentary but associated partial skeleton	An unenlagiine.
Llukalkan ^[12]	L. aliocranianus	La Invernada site.		A partial skull.	An abelisaur.
Neuquenornis^[3]	N. volans		Upper	A skull and a partial postcranial remains.	A enantiornithine bird.
Patagopteryx	P. eferrariisi		Upper		The oldest known flightless bird.
Tratayenia^[13]	T. rosalesi			A well-preserved partial skeleton	A megaraptoran theropod.
Velocisaurus^[12]	V. unicus				A noasaur.
Viavenator^[12]	V. exxoni				An abelisaur.

References

^ ^a ^b ^c Sánchez et al., 2006
^ Fossa Mancini et al., 1938
^ ^a ^b ^c ^d ^e Leanza et al., 2004
^ Martinelli et al., 2012
^ Lio et al., 2018
^ Filippi et al., 2018a
^ Coria et al., 2019
^ Rozadilla, Sebastián; Agnolín, Federico; Manabe, Makoto; Tsuihiji, Takanobu; Novas, Fernando E. (September 2021). "Ornithischian remains from the Chorrillo Formation (Upper Cretaceous), southern Patagonia, Argentina, and their implications on ornithischian paleobiogeography in the Southern Hemisphere". Cretaceous Research. 125: 104881. Bibcode:2021CrRes.12504881R. doi:10.1016/j.cretres.2021.104881. ISSN 0195-6671.
^ Cruzado Caballero et al., 2019
^ Filippi, Leonardo S.; Juárez Valieri, Rubén D.; Gallina, Pablo A.; Méndez, Ariel H.; Gianechini, Federico A.; Garrido, Alberto C. (2023). "A rebbachisaurid-mimicking titanosaur and evidence of a Late Cretaceous faunal disturbance event in South-West Gondwana". Cretaceous Research. 154. doi:10.1016/j.cretres.2023.105754. ISSN 0195-6671.
^ Porfiri, Juan D.; Baiano, Mattia A.; dos Santos, Domenica D.; Gianechini, Federico A.; Pittman, Michael; Lamanna, Matthew C. (2024-06-14). "Diuqin lechiguanae gen. et sp. nov., a new unenlagiine (Theropoda: Paraves) from the Bajo de la Carpa Formation (Neuquén Group, Upper Cretaceous) of Neuquén Province, Patagonia, Argentina". BMC Ecology and Evolution. 24 (1): 77. doi:10.1186/s12862-024-02247-w. ISSN 2730-7182. PMID 38872101.
^ ^a ^b ^c Filippi et al., 2018b
^ Porfiri et al., 2018

Bibliography

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Cruzado Caballero, P.; Gasca, J.M.; Filippi, L.S.; Cerda, I.; Garrido, A.C. (2019). "A new ornithopod dinosaur from the Santonian of Northern Patagonia (Rincón de los Sauces, Argentina)". Cretaceous Research. 98: 211–229. Bibcode:2019CrRes..98..211C. doi:10.1016/j.cretres.2019.02.014. S2CID 133830733.
Filippi, L.S.; Barrios, F.; Garrido, A.C. (2018a). "A new peirosaurid from the Bajo de la Carpa Formation (Upper Cretaceous, Santonian) of Cerro Overo, Neuquén, Argentina". Cretaceous Research. 83: 75–83. Bibcode:2018CrRes..83...75F. doi:10.1016/j.cretres.2017.10.021. Retrieved 2019-02-21.
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Lio, Gabriel; Agnolin, Federico L.; Martinelli, Agustín G.; Ezcurra, Martín D.; Novas, Fernando E. (2018). "New specimen of the enigmatic, Late Cretaceous crocodyliform Neuquensuchus universitas sheds light on the anatomy of the species". Cretaceous Research. 83: 62–74. Bibcode:2018CrRes..83...62L. doi:10.1016/j.cretres.2017.09.014. Retrieved 2019-02-21.
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