Unquillosaurus
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, 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. Classification. 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". Description. Based on the fragmentary fossil remains, it is estimated that "Unquillosaurus" may have had a total body length of about . Paleoecology. "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".