Name: »Xixian claw«
Length: 50 cm
Height: 20 cm
Weight: 0.5 kg
Time: Cretaceous (83 MYA)
Xixianykus (Greek for “Xixian claw”; pronounced shi-shi-ANN-ih-kuss) 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.
Xixianykus appears to have many adaptations towards a cursorial (running) lifetyle. It was about half a meter long but had 20 cm long legs and a short femur combined with a long tibia and metatarsus, which are good indicators of it being a fast runner.
Xixianykus is one of the newest alvarezsaurs, a family of feathered dino-birds that lived in Eurasia and the Americas during the middle to late Cretaceous periods. Judging by its unusually long legs (about a foot long, compared to a head-to-tail body size of only two feet or so) Xixianykus must have been an unusually fast predator, chasing down small, speedy animals at the same time as it avoided being eaten by larger carnivores. This is also one of the oldest alvarezsaurs yet discovered, which hints that these feathered dinosaurs may have originated in Asia and then spread west.
The authors of the new paper identified Xixianykus as a parvicursorine, or a specialized subset of alvarezaurids which may have relied on ants and termites for food. While the legs of these dinosaurs were well-adapted to running, their short and stout front limbs would have been used to rip open insect nests, and the authors of the paper propose that Xixianykus may have been like modern-day anteaters, moving between different nests every day to get enough food without wiping out the colonies it depended on. Further skeletal remains will be required to confirm this hypothesis, but based upon what the close relatives of Xixianykus were like, it is reasonable to assume that it shared the same traits related to a diet of ants and termites.
Genus: Xixianykus Xu et al, 2010
Species: X. zhangi Xu et al., 2010