The Jiufotang Formation deposited in Liaoning Province, northeastern China, is a well-studied Lower Cretaceous rock formation that holds a huge number of exceptionally preserved fossils. The Jiufotang is made up largely of sediments deposited in lake beds interspersed with volcanic ash. The Jiufotang and underlying Yixian Formation make up the famous Jehol Biota, known for its feathered dinosaurs including Sinosauropteryx, Yutyrannus, and thousands of bird specimens. The Jiufotang and Yixian Formations are a type of fossiliferous deposit known as a lagerstätte, meaning that they regularly preserve fossils in great detail.
A fossil bird specimen has recently been described by paleontologists Jennifer A. Peteya, Julia A. Clarke, Quanguo Li, Ke-Qin Gao, and Matthew D. Shawkey. The specimen itself is articulated and well-preserved, consisting of the majority of the skeleton and feathers preserved on the main slab and counterpart slab. Like many Mesozoic birds, it retains teeth, and hand claws, and lacks tail feathers that form a fan but instead had two stiff ribbon-like tail feathers. The skeleton's length is approximately 14 cm (5 inches) long, with a wingspan of 35-40 cm (14-16 inches), making it roughly the same size as a Common Starling.
Detailed examination of the skeleton indicates that it is a member of the bohaiornithid family. Bohaiornithids are known from several species, but appear to be limited in time and space to the Early Cretaceous of China. They are characterized by somewhat broad snouts with recurved teeth, and long foot claws. They are also considered to be predators of invertebrates and small vertebrates. Bohaiornithids are part of the enantiornithine radiation, the most common bird group throughout the Cretaceous. Enantiornithines are characterized by details of the shoulder and skeletal fusion, and most lack tail feather fans, but have the long ribbon-like tail feathers that are seen in this specimen. Enantiornithines, like most dinosaurs, went extinct at the end of the Cretaceous. Although the specimen is clearly a bohaiornithid, it isn't fully grown, so the authors declined to assign it to any known species, nor name a new species for the specimen.