Huallasaurus

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]

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
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Clade:	†Ornithischia
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 Bonaparte et al., 1984 Secernosaurus australis (Bonaparte et al., 1984) Wagner, 2001

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

Life restoration

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]