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Xiaotingia Temporal range: Bathonian–Oxfordian, ~165–153 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type specimen
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Anchiornithidae
Genus:	†Xiaotingia Xu et al., 2011
Type species
Xiaotingia zhengi Xu et al., 2011

Xiaotingia is a genus of anchiornithid theropod dinosaur from Middle Jurassic or early Late Jurassic deposits of western Liaoning, China, containing a single species, Xiaotingia zhengi.

Discovery

Xiaotingia is known from the holotype STM 27-2, an articulated and almost complete skeleton including the skull. It was probably collected in the Linglongta area, Jianchang, from the Tiaojishan Formation.

Etymology

Xiaotingia was first named by Xu Xing, You Hailu, Du Kai and Han Fenglu in 2011 and the type species is Xiaotingia zhengi. The generic name and specific name together honour paleontologist Zheng Xiaoting.

Description

Xiaotingia was morphologically similar to other anchiornithids. 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. Like Archaeopteryx 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.

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. If Xiaotingia could fly short distances it might also have used its hind limbs as wings.

Xiaotingia had a dentary tooth count probably less than 10 and teeth similar in morphology to those of basal avians.

Classification

The initial analysis by Xu et al. showed that Xiaotingia formed a clade with Archaeopteryx, Dromaeosauridae and Troodontidae to the exclusion of other groups traditionally seen as birds. Xu et al. therefore (re)defined the concepts of Deinonychosauria and Avialae to the extent that Archaeopteryx and Xiaotingia belonged to the Deinonychosauria in the clade Archaeopterygidae. This led to popular reports that "Archaeopteryx is no longer a bird", although Xu et al. noted that there are several competing definitions of the clade Aves currently in use, pointing out that their definitions are compatible with a traditional Aves with Archaeopteryx as a specifier. This phylogenetic hypothesis was challenged by an analysis using different methods published several months later however, in which Archaeopteryx was again recovered as an avialan, while Xiaotingia remained closely allied to Anchiornis within the Troodontidae. In 2012, an expanded and revised version of the initial analysis also found Archaeopteryx to be avialan and Anchiornis to be troodontid, but recovered Xiaotingia as the most primitive member of the clade Dromaeosauridae rather than a close relative of Anchiornis within Troodontidae.

Cladogram following the results of a phylogenetic study by Lefèvre et al., 2017.

In the 2017 re-evaluation of the Harlem Archaeopteryx specimen, Xiaotingia was found to be an anchiornithid, with this group being avialan. Hartman et al. (2019), which aimed to improve the state of theropod phylogenetic research, placed both Xiaotingia and Archaeopteryx in Deinonychosauria, the former as a troodontid and the latter a close relative of anchiornithids.

References

1. Zhang, H.; Wang, M.; Liu, X. (2008). "Constraints on the upper boundary age of the Tiaojishan Formation volcanic rocks in West Liaoning-North Hebei by LA-ICP-MS dating". Chinese Science Bulletin. 53 (22): 3574–3584. Bibcode:2008SciBu..53.3574Z. doi:10.1007/s11434-008-0287-4.
2. ^ Xing Xu; Hailu You; Kai Du & Fenglu Han (28 July 2011). "An Archaeopteryx-like theropod from China and the origin of Avialae" (PDF). Nature. 475 (7357): 465–470. doi:10.1038/nature10288. PMID 21796204. S2CID 205225790. Archived from the original (PDF) on 16 January 2016.
3. ^ Foth, C.; Rauhut, O.W.M. (2017). "Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs". BMC Evolutionary Biology. 17 (1): 236. doi:10.1186/s12862-017-1076-y. PMC 5712154. PMID 29197327.
4. ^ Ulysse Lefèvre, Andrea Cau, Aude Cincotta, Dongyu Hu, Anusuya Chinsamy, François Escuillié & Pascal Godefroit (2017). A new Jurassic theropod from China documents a transitional step in the macrostructure of feathers. The Science of Nature, 104: 74 (advance online publication). doi:10.1007/s00114-017-1496-y
5. "Feathers fly in first bird debate". BBC News. 27 July 2011.
6. Lee, M.S.Y. & Worthy, T.H. (2011). "Likelihood reinstates Archaeopteryx as a primitive bird". Biology Letters. 8 (2): 299–303. doi:10.1098/rsbl.2011.0884. PMC 3297401. PMID 22031726.
7. Senter, P.; Kirkland, J.I.; DeBlieux, D.D.; Madsen, S. & Toth, N. (2012). "New Dromaeosaurids (Dinosauria: Theropoda) from the Lower Cretaceous of Utah, and the Evolution of the Dromaeosaurid Tail". PLOS ONE. 7 (5): e36790. Bibcode:2012PLoSO...736790S. doi:10.1371/journal.pone.0036790. PMC 3352940. PMID 22615813.
8. Hartman, Scott; Mortimer, Mickey; Wahl, William R.; Lomax, Dean R.; Lippincott, Jessica; Lovelace, David M. (2019-07-10). "A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight". PeerJ. 7: e7247. doi:10.7717/peerj.7247. ISSN 2167-8359. PMC 6626525. PMID 31333906.

v t e Maniraptora
Kingdom: Animalia Phylum: Chordata Clade: Dinosauria Clade: Theropoda Clade: Maniraptoriformes Avemetatarsalia see Avemetatarsalia Theropoda see Theropoda Maniraptora see below↓
Maniraptora Maniraptora †Elopteryx? †Fukuivenator? †Kakuru? †Migmanychion †Yaverlandia? †Alvarezsauroidea Achillesaurus Aorun? Bannykus Bonapartenykus Haplocheirus Patagonykus Shishugounykus Tugulusaurus? Xiyunykus Alvarezsauridae Achillesaurus? Alnashetri Alvarezsaurus Bonapartenykus? Bradycneme Heptasteornis Patagonykus? Parvicursorinae Dzharaonyx Jaculinykus Khulsanurus Kol? Nemegtonykus Ondogurvel Parvicursor Qiupanykus Trierarchuncus Ceratonykini Albinykus Ceratonykus Xixianykus Mononykini Albertonykus Linhenykus Mononykus Shuvuuia †Therizinosauria Eshanosaurus? Falcarius Fukuivenator? Jianchangosaurus Lingyuanosaurus Therizinosauroidea Alxasaurus Beipiaosaurus Enigmosaurus Martharaptor Suzhousaurus Therizinosauridae Erliansaurus Erlikosaurus Nanshiungosaurus Neimongosaurus Nothronychus Paralitherizinosaurus Segnosaurus Therizinosaurus Pennaraptora †Oviraptorosauria see Oviraptorosauria Paraves see below↓
Paraves Paraves †Palaeopteryx? †Pneumatoraptor †Rahonavis †Scansoriopterygidae? Ambopteryx Epidexipteryx Scansoriopteryx Yi †Anchiornithidae Anchiornis Aurornis Caihong Eosinopteryx Fujianvenator Liaoningvenator? Ostromia Pedopenna Serikornis Xiaotingia Yixianosaurus †Archaeopterygidae Alcmonavis? Archaeopteryx Wellnhoferia Anchiornithidae? †Dromaeosauridae see Dromaeosauridae †Troodontidae see Troodontidae Avialae †Alcmonavis †Balaur? †Cretaaviculus? †Fukuipteryx †Overoraptor †Rahonavis? †Yandangornis †Zhongornis †Anchiornithidae? †Archaeopterygidae? †Scansoriopterygidae? †Jeholornithiformes Dalianraptor? Jeholornis Jixiangornis? Kompsornis Neimengornis Pygostylia †"Proornis" †Omnivoropterygidae? Omnivoropteryx Sapeornis †Confuciusornithidae Changchengornis Confuciusornis Eoconfuciusornis Yangavis †Jinguofortisidae Chongmingia Cratonavis Jinguofortis Ornithothoraces †Enantiornithes see Enantiornithes Euornithes see below↓
Euornithes Euornithes †Archaeorhynchus †Bellulornis †Brevidentavis †Changmaornis †Changzuiornis †Chaoyangia †Dingavis †Eogranivora †Gargantuavis? †Hollanda †Horezmavis †Jianchangornis †Jiuquanornis †Juehuaornis †Kaririavis †Meemannavis †Platanavis †Vorona †Wyleyia? †Xinghaiornis †Yumenornis †Zhongjianornis †Schizoouridae Mengciusornis Schizooura †Patagopterygiformes Alamitornis Kuszholia? Patagopteryx †Ambiortiformes Ambiortus Apsaravis? Palintropus? †Hongshanornithidae Archaeornithura Hongshanornis Longicrusavis Parahongshanornis Tianyuornis †Songlingornithidae Hollanda? Piscivoravis? Songlingornis Yanornis? Yixianornis? †Yanornithidae Abitusavis Similiyanornis Yanornis †Gansuidae? Changzuiornis Gansus Hollanda? Iteravis Khinganornis Shuilingornis Ornithurae †Antarcticavis? †Apatornis †Cerebavis †Gallornis †Guildavis †Iaceornis †Kookne †Limenavis †Tingmiatornis †Ichthyornithes Ichthyornis Janavis †Hesperornithes Baptornis Brodavis Chupkaornis Enaliornis Judinornis Pasquiaornis Potamornis Hesperornithidae Asiahesperornis Canadaga Fumicollis Hesperornis Parahesperornis †Vegaviidae Australornis? Maaqwi? Neogaeornis? Polarornis Vegavis †Cimolopterygidae Ceramornis Cimolopteryx Lamarqueavis? Aves / Neornithes see below↓
Aves / Neornithes Palaeognathae see Palaeognathae Neognathae Neoaves Galloanserae Anserimorphae see Anserimorphae Pangalliformes see Pangalliformes Incertae sedis †Asteriornis †Perplexicervix †Qinornis? †Dromornithidae Barawertornis Dromornis Genyornis Ilbandornis †Gastornithiformes Brontornis? Gastornis Dromornithidae? †Pelagornithidae Aequornis Caspiodontornis Cyphornis Dasornis Gigantornis Laornis? Lutetodontopteris Macrodontopteryx Manu? Odontopteryx Odontoptila Osteodontornis Palaeochenoides Pelagornis Proceriavis? Protodontopteryx Protopelicanus? Pseudodontornis Tympanonesiotes
See also: Archaeornithes Carinatae Deinonychosauria Odontognathae Odontornithes Sauriurae Unenlagiidae Category

• Late Jurassic dinosaurs of Asia
• Anchiornithidae
• Feathered dinosaurs
• Transitional fossils
• Fossil taxa described in 2011
• Taxa named by Xu Xing
• Paleontology in Liaoning
• Dinosaurs of China