Bajo de la Carpa Formation

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]

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	38.8°S 68.8°W / -38.8; -68.8
Approximate paleocoordinates	43.4°S 49.8°W / -43.4; -49.8
Region	Neuquén & Río Negro Provinces
Country	Argentina
Extent	Neuquén Basin
Bajo de la Carpa Formation (Argentina)

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

Reptiles reported from the Bajo de la Carpa Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Lomalatachelys[4]	L. neuquina				A snake-necked turtle
Dinilysia	D. patagonica				A Snake
Paleochelco[5]	P. occultato				A lizard
Podocnemidoidea[6]	Indeterminate.

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]

Crocodylomorphs

Crocodylomorphs reported from the Bajo de la Carpa Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Barrosasuchus	B. neuquenianus[7]	Sierra Barrosa	Upper	A skull articulated with the remaining skeleton, which consisted of both forelimbs, most of the vertebral column up to the sacra, one hindlimb, and semi-articulate osteoderms that obscured parts of the fossil	A peirosaurid notosuchian
Comahuesuchus	C. brachybuccalis	Universidad Nacional del Comahue	Upper	A holotype specimen	A Comahuesuchidae notosuchian.
Cynodontosuchus	C. rothi				A baurusuchid mesoeucrocodylian.
Lomasuchus	L. palpebrosus.				A peirosaurid notosuchian
Gasparinisuchus[8]	G. peirosauroides				A peirosaurid notosuchian
Kinesuchus	K. overoi[9]	Cerro Overo	Upper	A partial mandible	A peirosaurid notosuchian
Neuquensuchus	N. universitas [10]	Universidad Nacional del Comahue	Upper	Paratype specimens consist of a partially articulated partial postcranial skeleton and left leg bone.	A Mesoeucrocodylia crocodyliformes.
Notosuchus	N. lepidus				A notosuchian
	N. terrestris
Peirosaurus	P. torminni			A fragmentary skull and a partial postcranial skeleton.

Fish

Fish reported from the Bajo de la Carpa Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Rinconodus[11]	R. salvadori				A ceratodontid lungfish

Dinosaurs

Ornithischians

Ornithischians reported from the Bajo de la Carpa Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Ankylosauria[12]	Indetermidate.
Mahuidacursor[13]	M. lipanglef	Cerro Overo	Upper	A set of postcrania	An ornithopod.

Sauropods

Sauropods reported from the Bajo de la Carpa Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Bonitasaura	B. salgadoi			A partial sub-adult skeleton with a lower jaw, a partial vertebrae series, and limb bones.	A titanosaur.
Inawentu	I. oslatus	Rincón de los Sauces.		A partially articulated skeleton, including a nearly complete skull, Several vertebrae from the atlas to the end of the sacrum, and both ilia	A titanosaur.
Overosaurus	O. paradasorum		Upper	A fully articulated vertebral series consists of rib bones, dorsals, and ilium.	A titanosaur.
Rinconsaurus	R. caudamirus	Rincón de los Sauces.	Lower.	The fossil remains included vertebrae, limb bones, scapula, hip bones (pubis, ilium, and ischium) and several ribs.	A titanosaur.
Traukutitan[14]	T. eocaudata	Sitio Trauku.	Lower	A partial semi-articulated skeleton including both thigh bones and thirteen vertebrae from the anterior and middle tail.	A titanosaur.

Theropods

Theropods reported from the Bajo de la Carpa Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Achillesaurus	A. manazzonei	Paso Córdova	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	Boca del Sapo,	Upper	A set of postcrania	An Alvarezsaurid.
Diuqin[15]	D. lechiguanae	"the isthmus between the southeast coast of Lago Barreales and the northwest coast of Lago Mari Menuco"	Upper	A fragmentary but associated partial skeleton	An unenlagiine.
Llukalkan [16]	L. aliocranianus	La Invernada site.	Upper	A partial skull.	An abelisaur.
Neuquenornis[3]	N. volans	Boca del Sapo	Upper	A skull and a partial postcranial remains.	A enantiornithine bird.
Patagopteryx	P. deferrariisi	Boca del Sapo	Upper	A partial, incomplete skeleton consisting of 18 vertebrae, synsacrum, and much of the pectoral and pelvic girdles, wings, and hindlimbs.	The oldest known flightless bird.
Tratayenia[17]	T. rosalesi	Traytenia locality	Upper	A well-preserved partial skeleton	A megaraptoran theropod.
Velocisaurus[16]	V. unicus	Universidad Nacional del Comahue	Upper	A set of limb elements.	A noasaur.
Viavenator[16]	V. exxoni	La Invernada	Upper	A partial skeleton	An abelisaur.

See also

• List of fossil sites
• List of dinosaur bearing rock formations
• Mata Amarilla Formation, contemporaneous formation of the Austral Basin