Xixianykus
Encyclopedia
Xixianykus is a genus
of alvarezsauroid theropod dinosaur
from the late Cretaceous
period of China
. It was discovered in Xixia County
in Henan
, China
. It is among the oldest of the derived alvarezsauroids, the parvicursorines, dated to the Santonian
-Coniacian
as opposed to other parvicursorines, which are either Campanian
or Maastrichtian
.
(running) lifetyle. It was about 50 centimetres (19.7 in) long but had 20 centimetres (7.9 in) long legs and a short femur
combined with a long tibia
and metatarsus
, which are good indicators of it being a fast runner.
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 alvarezsauroid theropod 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 of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. It was discovered in Xixia County
Xixia County
Xixia County is a county of Nanyang, Henan, China, has an area of 3,452 square kilometers and a population of 420,000 as of 2002.-Controversy:...
in Henan
Henan
Henan , is a province of the People's Republic of China, located in the central part of the country. Its one-character abbreviation is "豫" , named after Yuzhou , a Han Dynasty state that included parts of Henan...
, China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
. It is among the oldest of the derived alvarezsauroids, the parvicursorines, dated to the Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
-Coniacian
Coniacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma...
as opposed to other parvicursorines, which are either 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 ...
or Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
.
Description
Xixianykus appears to have many adaptations towards a cursorialCursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
(running) lifetyle. It was about 50 centimetres (19.7 in) long but had 20 centimetres (7.9 in) long legs and a short femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
combined with a long tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
and metatarsus
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...
, which are good indicators of it being a fast runner.