Jeholornis

Jeholornis is a genus of Mesozoic bird that lived approximately 120 million years ago during the Early Cretaceous of China. Fossils of Jeholornis were discovered in the Jiufotang Formation in Hebei, China.

After Archaeopteryx and possibly Rahonavis, Jeholornis is the most primitive known bird. Jeholornis had a long tail and a few small teeth, and was approximately the size of a turkey, making it one of the largest birds known until the Late Cretaceous.

Description

A few fairly complete and well-preserved skeletal remains are known. The type specimen is in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. It is catalogued as IVPP V13274. It was reported in the journal Nature in 2002. Two more specimens were later accessioned by the IVPP as V 13550 and V 13553 and they were reported in the journal Naturwissenschaften in 2003. Another specimen is in the collection of the Liaoning Provincial Museum of Paleontology, and is catalogued as LPM 0193 it was reported as Shenzhouraptor in the journal The Geological Bulletin of China in 2002. Another specimen was reported as Jixiangornis in the Journal of Nanjing University (Natural Sciences).

The skeletons are generally similar to Archaeopteryx, but the tail structure is more like that of a dromaeosaur, and the coracoids are longer, more derived, and probably allowed for better flight capability. The flight apparatus skeleton was overall quite similar to that of Confuciusornis in form and function.

Feather traces on LPM 0193 show that unlike Confuciusornis, it had rounded, broad wings like a chicken or goshawk. The wing feathers were asymmetrical (as in modern flying birds) and up to 21 centimeters long, longer than than the forearm and hand combined.

The tail of several specimens preserve feathers at the end of the tail, shorter than those on the forelimbs. The construction of the tail was more solid than the tail of Archaeopteryx, more similar to the tails of dromaeosaurs. Additionally, the feathers of the tail are arranged in a fan stemming from the tip, as in dromaeosaurs but unlike the tail feathers of Archaeopteryx, which extend down the length of the tail. The tail of Jeholornis is also longer than that of Archaeopteryx, and is made up up up to 27 vertebrae in Jeholornis compared with 23 vertebrae in Archaeopteryx.

Classification and synonyms

Jeholornis contains only the type species, Jeholornis prima (meaning "first Jehol bird", in reference to the Jehol group of fossil beds where it was found, and the primitive appearance of the tail).. Zhou and Zhang classified Jeholornis in a new family, Jeholornithidae, of which it is the type genus, and the order Jeholornithiformes. No phylogenetic definitions for these groups were provided.

Naming dispute

Shenzhouraptor sinensis (the name of which is derived from "Shenzhou", an ancient name for China, "raptor", Latin for "violent plunder") was described in the July 2002 issue of Geological Bulletin of China by Ji et al., the same month as Jeholornis was described by Zhou and Zhang. Two of the diagnostic characteristics which could have distinguished Shenzhouraptor from Jeholornis were size and the absence of teeth, which may be attributed to age and preservational bias. The other major difference was a different number of caudal vertebrae, though Zhou and Zhang showed in 2003 that the specimen was missing several of the proximal caudals.

Several scientists have come to the conclusion that Jeholornis and Shenzhouraptor are specimens of the same species, and that one name takes precedence over the other. However, given that both names were published in print within days of each other (one in a monthly journal and one in a weekly), no consensus has been reached over which name should gain priority. The date on the article describing Jeholornis was July 25th, 2002. The paper describing Shenzhourptor was available in print on or before July 23rd, 2002. In 2003, Ji and colleagues made Jeholornis a junior synonym of Shenzhouraptor. In 2006, Zhou and Zhang argued that Jeholornis should have priority because it was published in a weekly journal, and that the ICZN gives priority to these over monthly journals.

In a 2006 study, Zhou and Zhang also classified Jixiangornis as junior synonym of Jeholornis.

Paleobiology

The type fossil of Jeholornis preserves seeds in the area of the crop. The seeds belong to the conifer form genus Carpolithus, thus it is uncertain what exact lineage of plant they represent. The Jeholornis specimen, while about three-quarters the size of the Shenzhouraptor, had small teeth in the upper jaw, whereas no teeth were visible in the latter. Two other specimens, IVPP V13353 and the aforementioned V13350 are smaller still and most certainly immature birds; they both have teeth. In the Shenzhouraptor type, the dentary and anterior skull are poorly preserved and this makes it impossible to say whether there were any teeth . The jaw is deep, the dentaries are well fused, and the teeth are reduced, and all indicate a specialized seed - feeding habit for Jeholornis.

Translation

The word "Jeholornis" occurs as such in the following languages: English, German, French, Italian, Dutch.

Translation(s) in other languages: Spanish: Shenzhouraptor, Polish: Shenzhouraptor, Portuguese: Shenzhouraptor sinensis, Chinese: 热河鸟.