Temporal range: Campanian
Unquillosaurus (meaning "Unquillo river lizard") is a genus of possible maniraptoran or carnosaurian theropod dinosaur from the Late Cretaceous Los Blanquitos Formation of Salta Province, Argentina. The genus contains a single species, U. ceibalii, known only from a single fossilized pubis (a pelvic bone).
Discovery and naming
The holotype, PVL 3670-11, was found at Arroyo-Morterito in the Los Blanquitos Formation, dating to the Campanian. It consists of a left pubis, 514 millimetres (1.686 ft) long. The specimen was re-studied by Fernando Novas and Federico Agnolin in 2004, who concluded that the orientation of the pubis had been misinterpreted: it pointed backwards, as was shown by the fossil still being attached to a displaced part of the pubic peduncle of the ilium.
The type species Unquillosaurus ceibalii was described by Jaime Eduardo Powell in 1979. The generic name, "Unquillosaurus," is derived from the river Unquillo and the Greek word, "sauros," meaning "lizard." The specific name, "ceibalii," refers to the town El Ceibal.
Powell originally assigned Unquillosaurus to the Carnosauria in 1986. In 2004, Novas and Agnolin concluded from the opisthopubic pelvic anatomy that Unquillosaurus was part of the Maniraptora or at least Maniraptoriformes, and likely closely related to either the Avialae or the bird-like Alvarezsauridae; perhaps it was itself a bird, a basal member of the Metornithes. In 2006 however, Novas stated that Unquillosaurus probably belonged to the maniraptoran clade Dromaeosauridae. Carrano et al. in 2012, placed the animal back in Carnosauria, specifically Carcharodontosauria, noting that the original interpretation was likely correct and that the animal has many similarities to Giganotosaurus.
Based on the fragmentary fossil remains, it is estimated that Unquillosaurus may have had a total body length of about 2–3 metres (6.6–9.8 ft).
Unquillosaurus is known from the Los Blanquitos Formation. The abelisaurid theropod Guemesia is also known from this formation, as well as fossils of what may belong to a species of Titanosaurus.
- HyperWorks Reference Software (1999), "The Dinosaur Encyclopedia: Unquillosaurus", viewed December 07, 2012.
- Novas and Agnolin, (2004). "Unquillosaurus ceibalii Powell, a giant maniraptoran (Dinosauria, Theropoda) from the Late Cretaceous of Argentina." Rev. Mus. Argentino Cienc. Nat., n.s. 6(1): 61-66.
- Powell, J.E. (1979). "Sobre una asociación de dinosaurios y otras evidencias de vertebrados del Cretácico Superior de la región de La Candelaria, Prov. de Salta, Argentina" ["On a dinosaur association and other evidinces of Upper Cretaceous vertebrates from the La Candelaria region, Salta Province, Argentina."] Ameghiniana, 16(1-2): 191-204. (In Spanish: English translation by Matthew Carrano, SUNY at Stony Brook, 8/99).
- Powell, J.E., 1986. Revision de los titanosauridos de America del Sur Argentina. Universidad Nacional de Tucuman, Argentina
- R.D. Martínez and F.E. Novas, 2006, "Aniksosaurus darwini gen. et sp. nov., a new coelurosaurian theropod from the early Late Cretaceous of central Patagonia, Argentina", Revista del Museo Argentino de Ciencias Naturales, nuevo serie 8(2): 243-259
- Matthew, Carrano (2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 10 (2): 211–300. doi:10.1080/14772019.2011.630927. S2CID 85354215.
- Agnolín, Federico L.; Cerroni, Mauricio A.; Scanferla, Agustín; Goswami, Anjali; Paulina-Carabajal, Ariana; Halliday, Thomas; Cuff, Andrew R.; Reuil, Santiago (2022-02-10). "First definitive abelisaurid theropod from the Late Cretaceous of Northwestern Argentina". Journal of Vertebrate Paleontology. 41 (4): e2002348. doi:10.1080/02724634.2021.2002348. ISSN 0272-4634. S2CID 246766133.
- Arroyo El Morterito at Fossilworks.org