Unquillosaurus
Encyclopedia
Unquillosaurus is a genus
of maniraptora
n dinosaur
from the late Cretaceous
Period, discovered in Argentina
. Known only from a single fossil
ized pubis
(a pelvic
bone), its total body length may have reached 2-3 meters (6-10 ft).
The type species
Unquillosaurus ceibalii was described by Jaime Eduardo Powell in 1979. The generic name is derived from the river Unquillo
. The specific name refers to the town El Ceibal.
The holotype
, PVL 3670-11, was found at Arroyo-Morterito in the Los Blanquitos Formation
dating from the Campanian
. It consists of a left pubis, 514 millimetres (1.7 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
.
Powell originally assigned Unquillosaurus to the Carnosauria
, in 1986. Novas and Agnolin in 2004 concluded from the opisthopubic pubis 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
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of maniraptora
Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea...
n dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period, discovered in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. Known only from a single fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
ized pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....
(a pelvic
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
bone), its total body length may have reached 2-3 meters (6-10 ft).
The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
Unquillosaurus ceibalii was described by Jaime Eduardo Powell in 1979. The generic name is derived from the river Unquillo
Unquillo
Unquillo is a city in the province of Córdoba, Argentina. It has 15,369 inhabitants as per the . It is located about 22 km north-northwest from the center of the provincial capital, Córdoba City, and 14 km east of Cosquín....
. The specific name refers to the town El Ceibal.
The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
, PVL 3670-11, was found at Arroyo-Morterito in the Los Blanquitos Formation
Los Blanquitos Formation
The Los Blanquitos Formation is a geological formation in Salta, Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Vertebrate paleofauna:...
dating from the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
. It consists of a left pubis, 514 millimetres (1.7 ft) long. The specimen was re-studied by Fernando Novas
Fernando Novas
Fernando Emilio Novas is an Argentine paleontologist working for the Comparative Anatomy Department of the Bernardino Rivadavia Natural History Argentine Museum in Buenos Aires...
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
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...
.
Powell originally assigned Unquillosaurus to the Carnosauria
Carnosauria
Carnosauria is a group of large predatory dinosaurs that lived during the Jurassic and Cretaceous periods. While it originally contained a wide assortment of giant theropods that were not closely related, the group has since been defined to encompass only the allosaurs and their closest kin...
, in 1986. Novas and Agnolin in 2004 concluded from the opisthopubic pubis that Unquillosaurus was part of the Maniraptora
Maniraptora
Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea...
or at least Maniraptoriformes
Maniraptoriformes
Maniraptoriformes is a clade of dinosaurs that contains ornithomimosaurs and maniraptors. This group was named by Thomas Holtz, who defined it as "the most recent common ancestor of Ornithomimus and birds, and all descendants of that common ancestor."...
, and likely closely related to either the Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
or the bird-like Alvarezsauridae
Alvarezsauridae
Alvarezsauridae is an enigmatic family of small, long-legged running dinosaurs. Although originally thought to represent the earliest known flightless birds, a consensus of recent work suggests that they are primitive members of the Maniraptora. Other work found them to be the sister group to the...
; 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
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Dromaeosauridae
Dromaeosauridae
Dromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
.