| Linhenykus | |
|---|---|
 | |
| Skeletal restoration, showing known parts in white | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Alvarezsauridae |
| Tribe: | †Mononykini |
| Genus: | †Linhenykus Xuet al., 2011 |
| Species: | †L. monodactylus |
| Binomial name | |
| †Linhenykus monodactylus Xuet al., 2011 | |
Linhenykus is an extinctgenus ofalvarezsauridtheropoddinosaur from theLate Cretaceous ofInner Mongolia,China. It is the mostbasal known member of theParvicursorinae. The genus gets its name fromLinhe, a city near the site where the fossil was first found and Greeknykus, "claw". Thespecific name is derived from Greekmonos, "single", anddaktylos, "finger", a reference to the fact that it is the only known non-avian dinosaur to have had but a single digit.
Linhenykus was a small dinosaur, measuring 50 cm (1.6 ft) long and weighing 500 g (18 oz).[1] Itsfemur length is 7 centimetres (2.8 in).[2]
Alvarezsauroids are known for their short forelimbs, each with a single greatly enlarged second digit. Although alvarezsaurids were once thought to have only a single digit on each forelimb, more recent evidence has shown that most species have reduced third and fourth digits.Linhenykus is the first known alvarezsaurid to have only a single, second digit.[2] Although a reduced thirdmetacarpal is present, thephalanges or finger bones of the third digit was entirely lost. The fourth metacarpal is not preserved in theLinhenykus holotype, but given that digit III is a reduced structure lacking phalanges, it is probable that this metacarpal is entirely absent inLinhenykus. Despite having the most reduced digits of anyalvarezsauroid,Linhenykus was shown bycladistic analysis to have been a basal form as is indicated by the fact that its enlarged digit is not as large or robust as with more advanced forms.[3]
Some scientists have suggestedLinhenykus, like other alvarezsaurids, wasinsectivorous, using its claws to dig into ant and termite nests, similar to modernanteaters.[4]
The fossil ofLinhenykus was collected byJonah N. Choiniere and Michael Pittman from the Late CretaceousWulansuhai Formation of Nei Mongol (Inner Mongolia), China. Biostratigraphic and lithographic correlations suggest that the formation dates to theCampanian andMaastrichtian stages, 75-71 Ma.Linhenykus is currently known from a partial skeleton,holotypeIVPP V17608, including cervical, dorsal, sacral and caudal vertebrae, forelimb, hindlimbs, and pelvis, and a referred completepes (anatomy).[5] The genus was first described and named in theProceedings of the National Academy of Sciences byXu Xing, Corwin Sullivan, Pittman, Choiniere, David Hone, Paul Upchurch, Tan Qingwei, Xiao Dong, Lin Tan and Han Fenglu in2011.[2] In 2013, an osteological monograph of the genus was published which included a quantitative analysis of alvarezsauroid biogeography.[6] The latter found statistically significant biogeographic reconstructions suggesting a dominant role for sympatric (or ‘within area’) events, combined with a mix of vicariance, dispersal and regional extinction.
It has been suggested thatLinhenykus may be a junior synonym ofParvicursor,[7] but this interpretation was rejected by the original authors[8] and has not been adopted in subsequent research on alvarezsauroids.[9]
Thecladogram below shows the phylogenetic position among alvarezsaurids following Makovicky, Apesteguía and Gianechini (2012).[9]
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