Zhongornis
Encyclopedia
Zhongornis is a genus
of primitive birds that lived during the Early Cretaceous. It was found in rocks of the Yixian Formation
in Lingyuan City (China
), and described by Gao et al. in 2008.
Zhongornis has only one described species, Zhongornis haoae. The only specimen is a fossil slab and counterslab numbered D2455/6. It is in the collection of the Dalian Natural History Museum. It is a fairly complete skeleton about eight centimeters in length. Pores in the bones and unfused sutures in the skeleton indicate that the specimen was a juvenile, but the authors believe that it was developed enough to erect a new taxon
on the basis of its unique morphological characters. There are feather impressions preserved on the right hand and also probable tail feathers preserved near the left foot. Zhongornis had a beaked mouth with no teeth. The tail is proportionately short, has thirteen vertebrae, and no pygostyle. The third finger has only two phalangeal bones, unlike non - avian dinosaurs and Confuciusornis
, and more like Enantiornithes
and more advanced birds. These features and a cladistic analysis indicate that Zhongornis is the sister group to all pygostylia
, meaning that it is intermediate between long - tailed Avialae
like Archaeopteryx
and more advanced taxa like Confuciusornis.
, which had reduced third fingers and tails fused into rigid pygostyle
s. Zhonghornis is the only fossil ever found that seems to be intermediate in these features. It appears to have one less bone in the third finger than Archaeopteryx, and one more than Longipteryx
, suggesting that it is an intermediate between the two.. Zhongornis also seems to be intermediate in its tail anatomy. It has only thirteen caudal vertebrae, far less than the 22 in Archaeopteryx. None of the vertebral centra are fused, but the last four do form a continuous lateral flange, implying that this specimen had an incipient pygostyle. Previous to this fossil Sanz et al. (1992) suggested that the evolution of the pygostyle may have proceeded as the numerous vertebrae of the tail became very small and highly ankylosed. Zhongornis suggests that shortening of the tail, and a large reduction in the number of vertebrae, preceded the origin of the pygostyle in the evolution of at least one bird lineage.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of primitive birds that lived during the Early Cretaceous. It was found in rocks of the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
in Lingyuan City (China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
), and described by Gao et al. in 2008.
Zhongornis has only one described species, Zhongornis haoae. The only specimen is a fossil slab and counterslab numbered D2455/6. It is in the collection of the Dalian Natural History Museum. It is a fairly complete skeleton about eight centimeters in length. Pores in the bones and unfused sutures in the skeleton indicate that the specimen was a juvenile, but the authors believe that it was developed enough to erect a new taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
on the basis of its unique morphological characters. There are feather impressions preserved on the right hand and also probable tail feathers preserved near the left foot. Zhongornis had a beaked mouth with no teeth. The tail is proportionately short, has thirteen vertebrae, and no pygostyle. The third finger has only two phalangeal bones, unlike non - avian dinosaurs and Confuciusornis
Confuciusornis
Confuciusornis is a genus of primitive crow-sized birds from the Early Cretaceous Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago...
, and more like Enantiornithes
Enantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
and more advanced birds. These features and a cladistic analysis indicate that Zhongornis is the sister group to all pygostylia
Pygostylia
Pygostylia is a group of birds which includes Confuciusornis and all of the more derived birds; the Ornithothoraces. Chiappe defined the Pygostylia as "the common ancestor of the Confuciusornithidae and Neornithes plus all its descendants". This is a node-based definition.Chiappe united the...
, meaning that it is intermediate between long - tailed Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
like Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
and more advanced taxa like Confuciusornis.
Evolutionary significance
Zhongornis provides important anatomical information about the evolutionary transition from primitive basal Avialae like Archaeopteryx, which had a long bony tail and a dinosaur-like third finger, to the more advanced birds like the EnantiornithesEnantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
, which had reduced third fingers and tails fused into rigid pygostyle
Pygostyle
Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these....
s. Zhonghornis is the only fossil ever found that seems to be intermediate in these features. It appears to have one less bone in the third finger than Archaeopteryx, and one more than Longipteryx
Longipteryx
Longipteryx is a genus of prehistoric bird which lived during the Early Cretaceous . It contains a single species, Longipteryx chaoyangensis. Its remains have been recovered from the Jiufotang Formation at Chaoyang in Liaoning Province, People's Republic of China...
, suggesting that it is an intermediate between the two.. Zhongornis also seems to be intermediate in its tail anatomy. It has only thirteen caudal vertebrae, far less than the 22 in Archaeopteryx. None of the vertebral centra are fused, but the last four do form a continuous lateral flange, implying that this specimen had an incipient pygostyle. Previous to this fossil Sanz et al. (1992) suggested that the evolution of the pygostyle may have proceeded as the numerous vertebrae of the tail became very small and highly ankylosed. Zhongornis suggests that shortening of the tail, and a large reduction in the number of vertebrae, preceded the origin of the pygostyle in the evolution of at least one bird lineage.