''Shuvuuia'' is a genus of bird-like theropod dinosaur from the late Cretaceous period of Mongolia. It is a member of the family

Alvarezsauridae Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, they are now thought to be an early diverging branch of maniraptoran theropods. Alvarezsaurids were highly ...

, small coelurosaurian dinosaurs which are characterized by short but powerful forelimbs specialized for digging. The type (and only known) species is ''Shuvuuia deserti'', or "desert bird".Chiappe, L.M., Norell, M. A., and Clark, J. M. (1998). "The skull of a relative of the stem-group bird ''Mononykus''." ''Nature'', 392(6673): 275-278. The name ''Shuvuuia'' is derived from the Mongolian word ''shuvuu'' (шувуу) meaning "bird".

Description

''Shuvuuia'' was a small and lightly built animal. At in length and in body mass, it is one of the smallest known non-avian dinosaurs. The skull is lightly built with long and slender jaws and minute teeth. ''Shuvuuia'' is unique among non-avian theropods in the skull's ability to perform

prokinesis Cranial kinesis is the term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaw. It is usually taken to mean relative movement between the upper jaw and the braincase. ...

, that is, it could flex its upper jaw independently of its braincase. The hindlimbs of ''Shuvuuia'' were long, slender, and short-toed, which may indicate significant running capabilities. The forelimbs, however, were unusually short and powerfully constructed. Although originally ''Shuvuuia'' and other alvarezsaurids were thought to have only a single digit on the front limb, newer specimens show the presence of reduced second and third fingers in addition to the massively enlarged thumb known from previous specimens.Suzuki, S, L. Chiappe, G. Dyke, M. Watabe, R. Barsbold and K. Tsogtbaatar (2002). "A new specimen of ''Shuvuuia deserti'' Chiappe et al., 1998, from the Mongolian Late Cretaceous with a discussion of the relationships of alvarezsaurids to other theropod dinosaurs." ''Contributions in Science (Los Angeles)'', 494: 1-18 Fossils of ''Shuvuuia'' are currently known from two locations within the Djadochta Formation: Ukhaa Tolgod and Tögrögiin Shiree. These sites are thought to be about 75 million years old (late Campanian age). Contemporary genera included '' Velociraptor'' and '' Protoceratops''.

Paleobiology

Nocturnal adaptations and diet

Like other alvarezsaurids, ''Shuvuuia'' may have used its forelimbs to open insect nests, and its slender, unusually mobile jaws to probe after such prey. However, new research based on analysis of the theropod's ears suggests that it was actually an owl-like, nocturnal hunter which used its strong legs to run down prey, and its arms to dig small prey such as insects and mammals out of burrows and shrubs; its lagena is about the same size as that of barn owls, giving it superb hearing in addition to its fantastic night vision (analyzed by looking at its

scleral ring Sclerotic rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for mammals and crocodilians. They can be made up of single bones or multiple segments and take their name from the sclera. They are bel ...

) allowing it to potentially hunt in complete darkness, unlike other theropods to which it has been compared, such as the apparently diurnal '' Dromaeosaurus'' and '' Tyrannosaurus''.

Feathers

Specimen IGM 100/977 of ''Shuvuuia'' was found surrounded by small, hollow, tube-like structures resembling the rachis (central vane) of modern bird feathers. Though highly deteriorated and poorly preserved, biochemical analyses later showed that these structures contain decay products of the protein beta-keratin, and more significantly, the ''absence'' of alpha-keratin. While beta-keratin is found in all integumentary (skin and feather) cells of reptiles and birds, only bird feathers completely lack alpha-keratin. These findings show that, though poorly preserved, ''Shuvuuia'' likely possessed a coat of feathers.Schweitzer, M.H., J.A. Watt, R. Avci, L. Knapp, L. Chiappe, M. Norell & M. Marshall. (1999). "Beta-keratin specific immunological reactivity in feather-like structures of the Cretaceous alvarezsaurid, ''Shuvuuia deserti''." ''Journal of Experimental Zoology'' (Mol Dev Evol), 285: 146-157.

References

{{Taxonbar, from=Q134230 Alvarezsaurids Late Cretaceous dinosaurs of Asia Feathered dinosaurs Taxa named by Mark Norell Fossil taxa described in 1998 Taxa named by Luis M. Chiappe Djadochta fauna