Unquillosaurus

• Salta, Argentina ( Lot Blanquitos Formation)

• Unquillosaurus ceibalii

Unquillosaurus was a theropod dinosaur that probably belongs to the group Dromaeosauridae. Of this genus is so far only a single bone known - a pubis ( pubic ), which was discovered in the Argentine province of Salta and 72-66 million years old is ( Maastrichtian, Upper Cretaceous ).

Features

The pubic bone found is 51 cm long, the entire animal could have reached about 3 feet in length. This finding shows a series of derived (modern) features: for example, the pubic bone was rotated backwards ( ophistopubic ). The lower end of the pubis ( Pubic boot) was shortened craniocaudal, its length is less than 30% of the total length of the pubic bone. In addition, the Pubic boot proximodistal was relatively high. These derived features are also found in early birds, indicating that Unquillosaurus was closely related to the birds. From other theropods to Unquillosaurus can distinguish in particular by a deep channel at the front end of the pubic bone.

System

Originally took Jaime Eduardo Powell ( 1979) due to the size of the bone that it was a representative of the Carnosaurier at Unquillosaurus, a group to which at that time the most well-known large theropods were counted. Fernando Novas and Federico Agnolin (2004) studied the fossil again and came to the conclusion that the Unquillosaurus Coelurosauria group Metornithes belongs, together with the Alvarezsauriden, the Therizinosauroideen, the Oviraptorosauriern, the Deinonychosauriern and the birds. Within the Metornithes Unquillosaurus could belong to any of the Dromaeosauridae, the researchers said. Today, the taxon Metornithes is considered invalid and is no longer used. Other studies - Norell and Makovicky ( 2004) and Martinez and Novas (2006) - see in Unquillosaurus also a possible Dromaeosauriden.

Fund, Research History and naming

The so far only find dates back to the Arroyo Morterito -locality, a locality at El Ceibal in the southern end of the Sierra de la Candelaria in the southeast of the Argentine province of Salta. From this locality two other dinosaur species could be detected in addition to Unquillosaurus - the sauropod Laplatasaurus sp. and a further, but an indefinite sauropod. The excavations at the Arroyo Morterito locality were completed in 1975. Stratigraphically, the reference is part of the upper portion of Lot Blanquitos formation, a layer member of the Salta Group, which consists of red to orange continental sandstones and conglomerates.

The Fund is a left pubis ( holotype, specimen number PVL 3670-11 ). He was described in 1979 along with the remains of sauropod Jaime Eduardo Powell for the first time scientifically. The name Unquillosaurus has the Río Unquillo, a river in the catchment area of ​​the locality is situated. The Style epithet ceibalii has El Caibal, the place, the reference is the closest. In 2004, Fernando Novas published and Federico Agnolin reexamination of Unquillosaurus.