Unenlagia

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Maniraptora > Pennaraptora > Paraves > Dromaeosauridae (?) > Unenlagiinae

Overview: Unenlagia was long seen as a somewhat mysterious dinosaur. Fossils of the animal were first described in 1997, having been found in Argentina’s Portezuelo Formation, dated to the Late Cretaceous. Recovered bones included the pelvis, some leg bones, bits of vertebrae, ribs and part of the shoulder. All of these remains shared traits in common with birds, so Unenlagia was seen by its describers as one of the non-avian dinosaurs most closely related to proper birds. This idea is reflected by its generic name, meaning “half-bird” in the local Mapuche language of the region. In some later studies, Unenlagia was associated with the “raptor” family Dromaeosauridae, so for a time, many reconstructions depicted it as a creature similar in appearance to dinosaurs such as Deinonychus or Velociraptor, but this has since been proven inaccurate.

Currently, paleontologists classify Unenlagia within a subfamily called the Unenlagiinae. Other taxa probably belonging to the group includes Austroraptor and Buitreraptor. Most are known from the southern hemisphere, but a few potential northern members are also known. Unenlagiines are often classified as an early diverging subfamily within the aforementioned Dromaeosauridae, but in some studies, they are seen as relatives of dromaeosaurs, but not as true members of the family. If the latter is true, then they are a subfamily within the proposed family Unenlagiidae (which may also contain dinosaurs like Halszkaraptor, in their own subfamily). Either way, unenlagiines are set apart by a few unique traits. They tended to have long, slender jaws, lightly built bodies and shorter arms. Traditional dromaeosaur traits like enlarged toe claws were also present on these animals.