''Unquillosaurus'' (meaning "Unquillo river lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of possible

maniraptora Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to ''Ornithomimus velox''. It contains the major subgroups Avialae, Deinonychosauria, Oviraptoros ...

n or

carnosaurian Carnosauria is an extinct large group of predatory dinosaurs that lived during the Jurassic and Cretaceous periods. Starting from the 1990s, scientists have discovered some very large carnosaurs in the carcharodontosaurid family, such as ' ...

theropod

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

Los Blanquitos Formation of Salta Province,

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The genus contains a single species, ''U. ceibalii'', known only from a single fossilized pubis (a

pelvic The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The p ...

bone).HyperWorks Reference Software (1999),
The Dinosaur Encyclopedia: ''Unquillosaurus''
, viewed December 07, 2012.

Discovery and naming

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

, PVL 3670-11, was found at Arroyo-Morterito in the Los Blanquitos Formation, dating to the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

. It consists of a left pubis, long. The specimen was re-studied by

Fernando Novas Fernando Emilio Novas (born 1960) is an Argentine paleontologist working for the Comparative Anatomy Department of the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires, Argentina.

and

Federico Agnolin Federico (; ) is a given name and surname. It is a form of Frederick, most commonly found in Spanish, Portuguese and Italian. People with the given name Federico Artists * Federico Ágreda, Venezuelan composer and DJ. * Federico Aguilar Alcuaz, ...

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.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. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

''Unquillosaurus ceibalii'' was described by Jaime Eduardo Powell in 1979. The generic name, "''Unquillosaurus''," is derived from the river

Unquillo Unquillo is a city in the province of Córdoba, Argentina. It has 18,483 inhabitants as per the . It is located about 28 km north-northwest from the center of the provincial capital, Córdoba City, and 14 km east of Cosquín. Unquillo ...

and the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word, "sauros," meaning "lizard." The specific name, "''ceibalii''," refers to the town

El Ceibal Seibal (), known as El Ceibal in Spanish, is a Classic Period archaeological site of the Maya civilization located in the northern Petén Department of Guatemala, about 100 km SW of Tikal. It was the largest city in the Pasión River regio ...

.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).

Classification

Powell originally assigned ''Unquillosaurus'' to the

Carnosauria Carnosauria is an extinct large group of predatory dinosaurs that lived during the Jurassic and Cretaceous periods. Starting from the 1990s, scientists have discovered some very large carnosaurs in the carcharodontosaurid family, such as '' G ...

in 1986. In 2004, Novas and Agnolin concluded from the opisthopubic pelvic anatomy that ''Unquillosaurus'' was part of the

Maniraptora Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to ''Ornithomimus velox''. It contains the major subgroups Avialae, Deinonychosauria, Oviraptoros ...

or at least Maniraptoriformes, and likely closely related to either the

Avialae Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative definitions are occasionally use ...

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 Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

. Carrano et al. in 2012, placed the animal back in Carnosauria, specifically

Carcharodontosauria Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Metriacanthosauridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae. Allosauroids, alongside the family Megalosauroidea, were among t ...

, noting that the original interpretation was likely correct and that the animal has many similarities to ''

Giganotosaurus ''Giganotosaurus'' ( ) is a genus of theropod dinosaur that lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period, approximately 99.6 to 95 million years ago. The holotype specimen was discovered in th ...

''.

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 Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are foun ...

theropod '' Guemesia'' is also known from this formation, as well as fossils of what may belong to a species of ''

Titanosaurus ''Titanosaurus'' (; ) is a dubious genus of sauropod dinosaurs, first described by Richard Lydekker in 1877.R. Lydekker. (1877). Notices of new and other Vertebrata from Indian Tertiary and Secondary rocks. ''Records of the Geological Survey of I ...

''.Arroyo El Morterito
at Fossilworks.org

References

{{Taxonbar, from=Q135633 Prehistoric tetanurans Campanian life Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Salta Basin Fossil taxa described in 1979 Taxa named by Jaime Powell

Discovery and naming

Classification

Description

Paleoecology

See also

References