Portezuelo Formation

Portezuelo Formation
Stratigraphic range: late Turonian–early Coniacian ~90.5–88.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Neuquén Group  Río Neuquén Subgroup
Underlies	Los Bastos Formation
Overlies	Lisandro Formation
Thickness	95–130 m (312–427 ft)
Lithology
Primary	Sandstone
Other	Conglomerate, limestone
Location
Coordinates	38.5°S 68.7°W / -38.5; -68.7
Approximate paleocoordinates	44.4°S 47.2°W / -44.4; -47.2
Region	Mendoza, Río Negro & Neuquén Provinces
Country	Argentina
Extent	Neuquén Basin
Type section
Named for	Sierra del Portezuelo
Portezuelo Formation (Argentina)

The Portezuelo Formation is a geologic formation of Late Cretaceous (Late Turonian to Early Coniacian) age, outcropping in the Mendoza, Río Negro and Neuquén provinces of Argentina.[1] It is the fourth-oldest formation in the Neuquén Group and the older of the two formations in the Río Neuquén Subgroup. Formerly, that subgroup was treated as a formation, and the Portezuelo Formation was known as the Portezuelo Member.[2]

Description

The type locality of the Portezuelo Formation is the mountain range known as Sierra del Portezuelo in Neuquén Province.[3] This formation conformably overlies the Lisandro Formation of the Río Limay Subgroup. In the top layers it grades into the Plottier Formation, the younger formation within the Río Neuquén Subgroup.

Sandstones and siltstones, probably deposited under fluvial conditions, make up the Portezuelo Formation. There are also occasional cemented claystone deposits, as well as numerous paleosols (fossil soils). The formation varies between 95 and 130 metres (312 and 427 ft) thick throughout its range.[2][4]

Fossil content

Many dinosaur fossils have recently been described from this formation, as well as remains of several other types of animals:

• teleosteid fish including Leufuichthys
• ceratodontiform lungfish including Chaoceratodus[5]
• abundant and diverse turtles including Baalemys,[6] Portezueloemys and a species of Prochelidella

• abelisauroid theropods (, a possible noasaurid and an abelisaurid)[1][7]

• several other theropods, including a modern, possibly galliform bird[8]
• ornithopods including possible iguanodonts

Dinosaurs

Ornithischians

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.

Ornithischians of the Portezuelo Formation
Taxa	Species	Locality	Stratigraphic unit	Material	Notes	Images
Macrogryphosaurus[9]	M. gondwanicus	The Mari Menuco lake		An incomplete skeleton of an adult individual which includes an almost complete vertebral column, eight cervical vertebrae, 14 dorsal vertebrae (complete series), six sacral vertebrae, thirteen caudal vertebrae, a cervical rib, eleven dorsal ribs; nine haemal arches, sternum, right and left pelvic girdles, and three thoracic mineralized plates.	An elasmarian ornithopod.

Sauropods

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.

Sauropods of the Portezuelo Formation
Taxa	Species	Locality	Stratigraphic unit	Material	Notes	Images
Baalsaurus	B. mansillai			A mostly complete right dentary	A titanosaur
Futalognkosaurus	F. dukei	Futalognko quarry		Atlas, axis, five anterior, four middle, and three poste-rior cervicals; 10 dorsals; ribs; complete sacrum; bothilia; right pubis and ischium; and one anterior caudal	A titanosaur
Malarguesaurus	M. florenciae		Upper and Lower parts	A holotype consists of tail vertebrae, chevrons, ribs, and limb bones	A titanosaur
Muyelensaurus	M. pecheni	Loma del Lindero site		A braincase including partial frontal and parietal, basioccipital, incomplete basipterigoid process, supraoccipital, exoccipital, basisphenoidals tubers, orbitosphenoids, and incomplete parasphenoids.	A titanosaur

Theropods

Theropods of the Portezuelo Formation
Taxa	Species	Locality	Stratigraphic unit	Material	Notes	Images
Elemgasem	E. nubilus	Sierra del Portezuelo	Lower	A holotype consists of partial axial and appendicular elements, including cervical and caudal vertebrae, right femur, left tibia, right and left fibula, left astragalus-calcaneum, metatarsals, and various pedal phalanges	A abelisaur	Elemgasem nubilus Megaraptor namunhuaiquii Neuquenraptor argentinus Pamparaptor micros Patagonykus puertai Unenlagia comahuensis
Megaraptor[8][10]	M. namunhuaiquii	Sierra del Portezuelo		A complete front limb, right ulna, and left manual phalanx.	A megaraptorid
Neuquenraptor[8][11]	N. argentinus	Sierra del Portezuelo		A holotype consists of fragments of cervical vertebra, dorsal ribs, haemal arches, left proximal radius, right femur and distal tibia, proximal tarsals, and most of the foot of the left hindlimb.	A dromaeosaurid
Pamparaptor [8][11]	P. micros	Baal Quarry		A holotype consists of three metatarsals, a complete second toe including the ungual, and two phalanges each from the third and fourth toes from the left foo	A dromaeosaurid
Patagonykus[8]	P. puertai	Los Barriales Lake.		An incomplete but well-preserved skeleton consists of multiple vertebrae, the coracoids, a partial forelimb, pelvic girdle, and hindlimbs	An alvarezsaur.
Unenlagia [8][11]	U. comahuensis	Sierra del Portezuelo	Upper	A partial skeleton lacking the skull but including vertebrae, a sacrum, ribs, chevrons, a scapula, a humerus, a partial pelvis, a femur and a tibia	A dromaeosaurid
	U. paynemili	Futalognko site	Upper	Several paratypes consists of a partial skeleton consisting of a humerus, vertebrae, claw, phalanx, and two pubes.

Reptiles

Reptiles of the Portezuelo Formation
Taxa	Species	Locality	Stratigraphic unit	Material	Notes	Images
Comahuesuchus	C. bonapartei[12]	The Futalognko quarry	Upper	A partially preserved (cranial-most region) of the right mandible	A notosuchian crocodylomorphs.
Lomasuchus	L. palpebrosus	Loma de la Lata			A peirosaurid notosuchian.
Patagosuchus	P. anielensis	Baal Quarry, Loma de la Lata		A fragmentary left dentary and splenial, the right maxilla and right jugal bone, a back vertebra, a back osteoderm and the right humerus.	A peirosaurid crocodyliform.

Pterosaurs

Pterosaurs of the Portezuelo Formation
Taxa	Species	Locality	Stratigraphic unit	Material	Notes	Images
Argentinadraco	A. barrealensis	Centro Paleontológico Lago Barreales	Upper	A single partial lower jaw, missing the rear end	An azdarchoid pterosaur.

See also

• List of fossil sites
• List of dinosaur bearing rock formations

References

1. Portezuelo Formation at Fossilworks.org
2. Sánchez et al., 2006
3. Wichmann, 1929
4. Leanza et al., 2004
5. Panzeri, K. M.; Guzmán, F. A. (2024). "Unveiling the histology and anatomy of the lungfish Chaoceratodus portezuelensis (Sarcopterygii: Dipnoi) from the Portezuelo and Cerro Lisandro formations (Upper Cretaceous) of Argentine Patagonia". Palaeontologia Electronica. 27 (2). 27.2.a42. doi:10.26879/1408.
6. Sarda, M.; Maniel, I. J. (2024). "A new chelid turtle with an ornamented bony shell (Pleurodira: Chelidae) from the Portezuelo Formation (Upper Cretaceous) of Patagonia, Argentina". Historical Biology: An International Journal of Paleobiology. doi:10.1080/08912963.2024.2437832.
7. Baiano, Mattia A.; Pol, Diego; Bellardini, Flavio; Windholz, Guillermo J.; Cerda, Ignacio A.; Garrido, Alberto C.; Coria, Rodolfo A (2022-09-05). "Elemgasem nubilus: a new brachyrostran abelisaurid (Theropoda, Ceratosauria) from the Portezuelo Formation (Upper Cretaceous) of Patagonia, Argentina". Papers in Palaeontology. 8 (5): e1462. Bibcode:2022PPal....8E1462B. doi:10.1002/spp2.1462.
8. Agnolin et al., 2006
9. Rozadilla, Sebastián; Cruzado-Caballero, Penélope; Calvo, Jorge O. (April 2020). "Osteology of Ornithopod Macrogryphosaurus gondwanicus (Dinosauria, Ornithischia) from the Upper Cretaceous of Patagonia, Argentina". Cretaceous Research. 108: 104311. Bibcode:2020CrRes.10804311R. doi:10.1016/j.cretres.2019.104311. S2CID 213679041.
10. Paulina-Carabajal and Currie, 2017
11. Porfiri et al., 2007
12. Kellner, Alexander & Figueiredo, Rodrigo & CALVO, JORGE. (2023). A new species of Comahuesuchus Bonaparte, 1991 (Crocodyliformes: Notosuchia) from the Upper Cretaceous of Neuquén, Lake Barreales, Patagonia, Argentina. Anais da Academia Brasileira de Ciências. 95. 10.1590/0001-3765202320230179. s.

Bibliography

• Agnolin, Federico L.; Novas, Fernando E.; Lio, Gabriel (2006). "Neornithine bird coracoid from the Upper Cretaceous of Patagonia". Ameghiniana. 43: 245–248. Retrieved 2019-02-16.
• Leanza, H.A.; Apesteguia, S.; Novas, F.E.; De la Fuente, M.S. (2004). "Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages". Cretaceous Research. 25 (1): 61–87. Bibcode:2004CrRes..25...61L. doi:10.1016/j.cretres.2003.10.005. Retrieved 2019-02-16.
• Paulina-Carabajal, Ariana; Currie, Philip (2017). "The braincase of the theropod dinosaur Murusraptor: osteology, neuroanatomy and comments on the paleobiological implications of certain endocranial features". Ameghiniana. 54 (5): 617–640. doi:10.5710/AMGH.25.03.2017.3062. hdl:11336/184065. Retrieved 2020-12-11.
• Porfiri, Juan D.; Calvo, Jorge Orlando; Dos Santos, Domenica Diniz; Juárez Valieri, Ruben D. (2007). New record of Neuquenraptor (Theropoda, Dromaeosauridae) from the Late Cretaceous of Patagonia. Jornadas Argentinas de Paleontología de Vertebrados. pp. 34R. Retrieved 2019-02-16.
• Sánchez, María Lidia; Heredia, Susana; Calvo, Jorge O. (2006). "Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén), Departamento Confluencia, Neuquén (Sedimentary paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquen Group), Confluencia, Neuquén)". Revista de la Asociación Geológica Argentina. 61: 3–18. Retrieved 2019-02-16.
• Wichmann, R (1929). "Los Estratos con Dinosaurios y su techo en el este del Territorio del Neuquén ("The dinosaur-bearing strata and their upper limit in eastern Neuquén Territory")". Dirección General de Geología, Minería e Hidrogeología Publicación. 32: 1–9.