| Yanornis Temporal range: Early Cretaceous, 120 Ma |
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| Life restoration | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | †Yanornithiformes |
| Family: | †Songlingornithidae |
| Genus: | †Yanornis |
| Species: | †Y. martini |
| Binomial name | |
| Yanornis martini Zhou & Zhang, 2001 |
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| Synonyms | |
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Yanornis is an extinct genus of omnivorous Early Cretaceous birds, thought to be closely related to the common ancestor of all modern birds. One species, Yanornis martini, has been described from fossils found in the Jiufotang Formation at Chaoyang, Western Liaoning province, PRC, and as of 2004 five specimens were known.[1] The age of the Jiufotang Formation is estimated to be early Aptian, about 120 million years ago. The genus name Yanornis is derived from the Ancient Chinese Yan dynasties, whose capital was at Chaoyang, and Ancient Greek ornis, "bird". The species Y. martini was named for avian paleontologist Larry Martin.
It was the size of a chicken,[2] had a long skull with about 10 teeth in the upper jaw and 20 teeth in the lower jaw, and was both able to fly and walk well, having a well-developed U-shaped furcula (wishbone). It ate a varied diet and was capable of switching between major food sources, including fish and seeds, as evidenced by some specimens which preserve large amounts of gastroliths in the stomach.[3] Its fish-eating and associated adaptations shows convergent evolution to the unrelated enantiornithine Longipteryx.[4]
The absence of the prefrontal bone and the non-diapsid skull place Yanornis into the Ornithurae which also includes the common ancestor of living birds. Similarly, its scapula and coracoid had evolved the basic shape and layout as in modern birds; enabling Yanornis to lift its wings far above its back for an efficient upstroke. It thus was a more efficient flyer compared to Enantiornithes (which have the modern condition in a less well-developed form), let alone Confuciusornis which like Archaeopteryx was only marginally able to perform an upstroke.[5] To allow for the necessarily large flight muscles, its sternum was longer than wide, again representing an essentially modern condition, as did many features of its arm skeleton.[6]
Yanornis gained notoriety when the front half of a fossil bird was combined with the tail of a Microraptor to make the paleontological forgery "Archaeoraptor". Upon discovering this, the bird half was described as Archaeovolans repatriatus, which was later found to be a junior synonym of Yanornis. See Archaeoraptor. Some studies have also found that the bird species Aberratiodontus wui is in fact a poorly preserved specimen of Yanornis martini, or at least a close relative,[7][8] an opinion which has been supported by subsequent reviews of enantiornithine taxonomy.[9]
In a 2006 study of early bird relationships, it was found that Yanornis, Yixianornis, and Songlingornis formed a monophyletic group; since Songlingornis was the first of these birds to be described, the family containing this group is Songlingornithidae.[10] The order Yanornithiformes has been erected to mark their distinctness from other early Ornithurae such as Gansus, but might be called Songlingornithiformes; especially if the present taxon is indeed a junior synonym of Songlingornis as sometimes proposed.[6]