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Huallasaurus; Temporal range: Late Cretaceous, ; ~85–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Reconstructed skeleton at Natural Sciences Museum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Neornithischia
Clade:	†Ornithopoda
Family:	†Hadrosauridae
Subfamily:	†Saurolophinae
Clade:	†Austrokritosauria
Genus:	†Huallasaurus; Rozadilla et al., 2022
Species:	†H. australis
Binomial name
	†Huallasaurus australis; (Bonaparte et al., 1984)
Synonyms
	Kritosaurus australis et al., 1984; Secernosaurus australis (Bonaparte et al., 1984) Wagner, 2001;

Huallasaurus (meaning "duck lizard") is an extinct genus of saurolophine hadrosaur from the Late Cretaceous Los Alamitos Formation of Patagonia in Argentina. The type and only species is H. australis. Originally named as a species of Kritosaurus in 1984,^[1] it was long considered a synonym of Secernosaurus^[2] before being recognized as its own distinct genus in a 2022 study, different from other members of Kritosaurini.^[3]

Discovery

The generic name, "Huallasaurus," combines "hualla," the Mapudungun word for "duck," and the Greek "sauros," meaning "lizard." The specific name, "australis," is derived from the Latin "australis," meaning "southern," after the discovery of the holotype specimen in southern Argentina.^[3]^[1]

Classification

Rozadilla et al. (2022) named Huallasaurus and the closely related Kelumapusaura, recovering them in a clade of entirely South American saurolophines.^[3] In the 2023 description of the South American hadrosauroid Gonkoken, Alarcón-Muñoz et al. recovered similar results, implementing a modified version of the phylogenetic matrix of Rozadilla et al. They named the clade containing Huallasaurus, Kelumapusaura, and other South American saurolophines as the Austrokritosauria, recovering it as the sister taxon to the Kritosaurini. The results of their phylogenetic analyses of Saurolophinae are displayed in the cladogram below:^[4]

Saurolophinae

	Wulagasaurus

	Acristavus

Maiasaura

	Probrachylophosaurus

	Brachylophosaurus

Austrokritosauria

Secernosaurus

Bonapartesaurus

	Kelumapusaura

	Huallasaurus

Kritosaurini

Kritosaurus

	Rhinorex

	Gryposaurus latidens

	Gryposaurus notabilis

	Gryposaurus monumentensis

Kamuysaurus

Prosaurolophus

	Saurolophus osborni

	Saurolophus angustirostris

	Laiyangosaurus

	Kerberosaurus

Shantungosaurus

	Edmontosaurus regalis

	Edmontosaurus annectens

Paleoecology

Huallasaurus is known from the Late Cretaceous Los Alamitos Formation of Río Negro Province, Argentina. Aeolosaurus rionegrinus, a titanosaurian sauropod, has also been named from this formation.^[3]

References

^ ^a ^b Bonaparte, José; Franchi, M.R.; Powell, J.E.; Sepulveda, E. (1984). "La Formación Los Alamitos (Campaniano-Maastrichtiano) del sudeste de Rio Negro, con descripcion de Kritosaurus australis n. sp. (Hadrosauridae). Significado paleogeografico de los vertebrados". Revista de la Asociación Geológica Argentina (in Spanish). 39 (3–4): 284–299.
^ Prieto–Marquez, Alberto; Salinas, Guillermo C. (2010). "A re–evaluation of Secernosaurus koerneri and Kritosaurus australis (Dinosauria, Hadrosauridae) from the Late Cretaceous of Argentina". Journal of Vertebrate Paleontology. 30 (3): 813–837. Bibcode:2010JVPal..30..813P. doi:10.1080/02724631003763508. S2CID 85814033.
^ ^a ^b ^c ^d Rozadilla, Sebastián; Brissón-Egli, Federico; Lisandro Agnolín, Federico; Aranciaga-Rolando, Alexis Mauro; Novas, Fernando Emilio (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.
^ Alarcón-Muñoz, Jhonatan; Vargas, Alexander O.; Püschel, Hans P.; Soto-Acuña, Sergio; Manríquez, Leslie; Leppe, Marcelo; Kaluza, Jonatan; Milla, Verónica; Gutstein, Carolina S.; Palma-Liberona, José; Stinnesbeck, Wolfgang; Frey, Eberhard; Pino, Juan Pablo; Bajor, Dániel; Núñez, Elaine; Ortiz, Héctor; Rubilar-Rogers, David; Cruzado-Caballero, Penélope (2023-06-16). "Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile". Science Advances. 9 (24): eadg2456. Bibcode:2023SciA....9G2456A. doi:10.1126/sciadv.adg2456. ISSN 2375-2548. PMC 10275600. PMID 37327335.