''Shuvuuia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of bird-like

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

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

from the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

period of

Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...

. 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

coelurosauria Coelurosauria (; from Greek, meaning "hollow-tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyra ...

n dinosaurs which are characterized by short but powerful forelimbs specialized for digging. The type (and only known) species is ''Shuvuuia deserti'', or "desert bird". 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; 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.; Chiappe, L.; Dyke, G.; Watabe, M.; Barsbold, R.; and Tsogtbaatar, K. (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 The Djadochta formation (sometimes transcribed and also known as Djadokhta, Djadokata, or Dzhadokhtskaya) is a highly fossiliferous geological formation in Central Asia, Gobi Desert, dating from the Late Cretaceous period, about 75 million ...

: Ukhaa Tolgod and Tögrögiin Shiree. These sites are thought to be about 75 million years old (late

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. Campa ...

age). Contemporary genera included ''

Velociraptor ''Velociraptor'' (; ) is a genus of small dromaeosaurid dinosaurs that lived in Asia during the Late Cretaceous epoch, about 75 million to 71 million years ago. Two species are currently recognized, although others have been assigned in th ...

'' and ''

Protoceratops ''Protoceratops'' (; ) is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 75 to 71 million years ago. The genus ''Protoceratops'' includes two species: ''P. andrewsi'' and the larger ''P. hellenik ...

''.

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 The scleral ring or sclerotic ring is a hardened ring of plates, often derived from bone, that is found in the eyes of many animals in several groups of vertebrates. Some species of mammals, amphibians, and crocodilians lack scleral rings. The ring ...

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

Dromaeosaurus ''Dromaeosaurus'' (; ) is a genus of Dromaeosauridae, dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period (middle late Campanian and Maastrichtian), sometime between 80 and 69 million years ago, in Alberta, Canada and th ...

'' and ''

Alioramus ''Alioramus'' (; meaning 'different branch') is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. It currently contains two species. The type species, ''A. remotus'' is known from a partial skull and three foo ...

''.

Feathers

Specimen IGM 100/977 of ''Shuvuuia'' was found surrounded by small, hollow, tube-like structures resembling the

rachis In biology, a rachis (from the [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the ''rachi ...

(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 Beta-keratin (β-keratin) is a structural protein found in the epidermis of reptiles, birds, and pangolins. Structure Beta-keratins were named due to their composition of stacked beta sheets in the epidermal stratum corneum, distinguishing th ...

, 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.

References

{{Taxonbar, from=Q134230 Alvarezsauridae Dinosaur genera Campanian dinosaurs Djadochta Formation Taxa named by Luis M. Chiappe Taxa named by Mark Norell Taxa named by James M. Clark Fossil taxa described in 1998 Dinosaurs of Mongolia