''Zhongjianornis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of beaked, pigeon-sized

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s from the early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

period of China. It is known from one fossil found at Jianchang, Liaoning Province, in rocks of the

Jiufotang Formation The Jiufotang Formation ( Chinese: 九佛堂组, pinyin: ''jiǔfótáng zǔ'') is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see ...

, representing the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

''Zhongjianornis yangi''. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

specimen is in the collection of the

Institute of Vertebrate Paleontology and Paleoanthropology The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name sugges ...

Beijing } Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...

, and the species ''Z. yangi'' is named for the IVPP's founder,

Yang Zhongjian Yang Zhongjian, also Yang Chung-chien (; 1 June 1897 – 15 January 1979), courtesy name Keqiang (), also known as C.C. (Chung Chien) Young, was a Chinese paleontologist and zoologist. He was one of China's foremost vertebrate paleontologists. H ...

.Li, D., Sulliven, C., Zhou, Z. and Zhang, Z. (2010). "Basal birds from China: a brief review." ''Chinese Birds'', 1(2): 83-96 This specimen is catalogued under the accession number IVPP V15900. It consists of a complete skeleton, possibly only missing a few tail vertebrae.

History and classification

''Z. yangi'' was initially believed to be the most primitive (though not earliest) bird species that completely lacked teeth, and one of the most basal birds known. It was described by Zhou, Zhang and Li, in a paper published in January 2010 (though the paper had appeared on the Internet during 2009).Zhou, Z., Zhang, F. and Li, Z. (2010). "A new Lower Cretaceous bird from China and tooth reduction in early avian evolution." ''Proceedings of the Royal Society B'', 277(1679): 219-227. They found that ''Zhongjianornis'' was more primitive than ''

Confuciusornis ''Confuciusornis'' is a genus of basal crow-sized avialan from the Early Cretaceous Period of the Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago. Like modern birds, ''Confuciusornis'' had a toothless beak, b ...

'', and that it predated the split between euornithean and enantiornithean birds. The authors also reported that ''Zhongjianornis'' shared features with very basal birds like ''

Jeholornis ''Jeholornis'' (meaning "Jehol bird") is a genus of avialans that lived between approximately 122 and 120 million years ago during the early Cretaceous Period in China. Fossil ''Jeholornis'' were first discovered in the Jiufotang Formation in ...

'', ''

Sapeornis ''Sapeornis'' is a monotypic genus of avialan which lived during the early Cretaceous period ( late Barremian to early Aptian, roughly 125-120 mya). ''Sapeornis'' contains only one species, ''Sapeornis chaoyangensis''. Description ''Sapeornis ...

'' and ''

'', including a highly expanded deltopectoral crest, and suggest that this was an early flight architecture that was replaced by an enlarged, keeled breastbone in more advanced birds. However, later analysis of the anatomy of ''Z. yangi'' cast doubt on this interpretation of the bird as very primitive. Research published in 2012 found that some of the apparently primitive features were due to poor preservation of the bones, and that ''Zhongjianornis'' is more similar in anatomy to primitive euornitheans like ''

Chaoyangia ''Chaoyangia'' is an extinct genus of euornithean birds, containing the single species ''Chaoyangia beishanensis''. This species is known from a single fossil specimen consisting of a partial skeleton including vertebra, ribs, hips, and upper l ...

'' and '' Schizooura''. A phylogenetic analysis showed that a very primitive position in the bird family tree for ''Z. yangi'' is unlikely given current evidence.O'Connor, J.K. and Zhou Z. (2012). "A redescription of ''Chaoyangia beishanensis'' (Aves) and a comprehensive phylogeny of Mesozoic birds." ''Journal of Systematic Palaeontology'', (advance online publication).

References

Prehistoric euornitheans Early Cretaceous birds of Asia Bird genera Fossil taxa described in 2010 Prehistoric birds of Asia Jiufotang fauna {{theropod-stub