| Xiaotingia | |
|---|---|
 | |
| Type specimen | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Anchiornithidae |
| Genus: | †Xiaotingia Xuet al.,2011 |
| Type species | |
| Xiaotingia zhengi Xuet al., 2011 | |
Xiaotingia is agenus ofparaviantheropoddinosaur, possibly ananchiornithid, fromMiddle Jurassic or earlyLate Jurassic deposits of westernLiaoning,China. It contains a single species,Xiaotingia zhengi.[2][3]
Xiaotingia is known from theholotypeSTM 27-2, an articulated and almost completeskeleton including theskull. It was probably collected in the Linglongta area,Jianchang, from theTiaojishan Formation.[2]
Xiaotingia was first named byXu Xing,You Hailu,Du Kai andHan Fenglu in2011 and thetype species isXiaotingia zhengi. The generic name andspecific name together honour paleontologistZheng Xiaoting.[2]
Xiaotingia was morphologically similar to otheranchiornithids. It was about 60 cm long and weighed an estimated 0.82 kg. It was a small feathered dinosaur that lived in an arboreal environment. LikeArchaeopteryx it had long forelimbs. Its femur was longer than its humerus, 84 mm compared to 71 mm, which might indicate that it stood on its hind limbs and could flap its forelimbs to achieve flight.[2]
Xiaotingia had feathers on its head, body, forelimbs and hind limbs. The feathers on the femur were quite long, measuring 55 mm. It also had long pennaceous feathers on its tibia and metatarsus. IfXiaotingia could fly short distances it might also have used its hind limbs as wings.[4]
Xiaotingia had a dentary tooth count probably less than 10 and teeth similar in morphology to those of basal avians.[2]
The initial analysis by Xuet al. showed thatXiaotingia formed aclade withArchaeopteryx,Dromaeosauridae andTroodontidae to the exclusion of other groups traditionally seen as birds. Xuet al. therefore (re)defined the concepts ofDeinonychosauria andAvialae to the extent thatArchaeopteryx andXiaotingia belonged to the Deinonychosauria in the cladeArchaeopterygidae.[2] This led to popular reports that "Archaeopteryx is no longer a bird",[5] although Xuet al. noted that there are several competing definitions of the clade Aves currently in use, pointing out that their definitions are compatible with a traditionalAves withArchaeopteryx as a specifier.[2] This phylogenetic hypothesis was challenged by an analysis using different methods published several months later however, in whichArchaeopteryx was again recovered as an avialan, whileXiaotingia remained closely allied toAnchiornis within the Troodontidae.[6] In 2012, an expanded and revised version of the initial analysis also foundArchaeopteryx to be avialan andAnchiornis to be troodontid, but recoveredXiaotingia as the most primitive member of the cladeDromaeosauridae rather than a close relative ofAnchiornis within Troodontidae.[7]
Cladogram following the results of a phylogenetic study by Lefèvreet al., 2017.[4]
In the 2017 re-evaluation of the HarlemArchaeopteryx specimen,Xiaotingia was found to be ananchiornithid, with this group being avialan.[3] Hartmanet al. (2019), which aimed to improve the state of theropod phylogenetic research, placed bothXiaotingia andArchaeopteryx in Deinonychosauria, the former as atroodontid and the latter a close relative of anchiornithids.[8] Foth et al. (2025) recoveredXiaotingia as a sister taxon ofAvialae, but outside anchiornithids.[9]
.jpg)
