Open Paleo

Huallasaurus

Rozadilla et al., 2021 WAH-yah-SOR-us

Duck lizard; from hualla, the Mapudungun word for duck, combined with Greek sauros (lizard)

83.6–66.0 million years ago Campanian–Maastrichtian, Late Cretaceous
Late Cretaceous stages

Huallasaurus 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, it was long considered a synonym of Secernosaurus before being recognized as its own distinct genus in a 2022 study, different from other members of Kritosaurini.

Diagnosis

  1. Maxilla with obliquely oriented, strongly posteriorly inclined ectopterygoid ridge
  2. Jugal with dorsoventrally low anterior process
  3. Postorbital with finger-like medial process forming anterior margin of supratemporal fenestra
  4. Dentary with ventrally concave shallow groove at anterior margin
  5. Postacetabular process bearing longitudinal groove on dorsal surface

Species

Huallasaurus australis (Bonaparte et al., 1984)

Type species

First named as Kritosaurus australis

From Latin 'australis' meaning 'southern', after the discovery of the holotype in southern Argentina.

Holotype
MACN-PV 2 , Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’
Material
Right prefrontal, left postorbital, partial sacrum with four fused centra, sacral vertebrae and ribs, middle caudal vertebrae, left and right sternals, right coracoid and scapula, left and right ilia, left and right ischia lacking distal shafts, left and right pubes, left femur and proximal right femur
Horizon
middle Los Alamitos Formation, Campanian–Maastrichtian, Late Cretaceous , 83.6–66.0 million years ago
Locality
Estancia Los Alamitos, Río Negro, Argentina Powell (1986) places the estancia's fauna in the lower section of the formation, against the describing paper's middle.

References

  1. Rozadilla, S.; Brissón Egli, F.; Agnolín, F. L.; Aranciaga Rolando, A. M.; Novas, F. E. (2021). 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. Informa UK Limited. doi:10.1080/14772019.2021.2020917 rozadilla2021a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length estimate.

    jones2026a
  3. Bonaparte, J. F.; Franchi, M. R.; Powell, J. E.; Sepúlveda, E. G. (1984). La Formación Los Alamitos (Campaniano-Maastrichtiano) del sudeste de Río Negro, con descripción de Kritosaurus australis n. sp. (Hadrosauridae). Significado paleogeográfico de los vertebrados. Revista de la Asociación Geológica Argentina 39(3-4): 284-299. Asociación Geológica Argentina.

    Erects the species as Kritosaurus australis and places the holotype in the middle sector of the formation at the Estancia Los Alamitos.

    bonaparte1984b
  4. Powell, J. E. (1986). Revisión de los titanosáuridos de América del Sur. Doctoral thesis, Universidad Nacional de Tucumán, Tucumán, Argentina.

    Unpublished doctoral thesis, 493 pp., as cited in Powell's own 2003 revision of it. The two are separate works: this thesis is in Spanish, while the revision published on it, Powell (2003), is in English. The thesis is retained here because the literature cites it as the first mention of several names, which as a thesis it did not make available.

    powell1986a
  5. Powell, J. E. (2003). Revision of South American Titanosaurid dinosaurs: palaeobiological, palaeobiogeographical and phylogenetic aspects. Records of the Queen Victoria Museum 111: 1-173.

    Lists Kritosaurus australis in the dinosaur fauna of Estancia Los Alamitos, Río Negro Province.

    powell2003a