File:Confuciusornis sanctus fossil bird (Yixian Formation, Lower Cretaceous; Sihetun Quarry, Liaoning Province, northeastern China) 3.jpg

Confuciusornis sanctus Hou et al., 1995 fossil bird from the Cretaceous of China (public display, Walter L. Gross III collection, Cincinnati Museum of Natural History and Science, Cincinnati, Ohio, USA)

Confuciusornis sanctus is a famous fossil bird from China. Many skeletons with preserved feathers have been found in the Jehol Lagerstätte, an Early Cretaceous lake deposit in North China having an abundance of well-preserved fossils, many with nonmineralizing parts still present. The most spectacular fossils in the Jehol Lagerstätte are feathered dinosaurs and early birds. The lake deposits are rich in volcanic sediments - the macrovertebrates were likely killed and buried by volcanic ash.

Confuciusornis has asymmetrical flight feathers and lacks teeth in its mouth, so it is considered the oldest known beaked bird. The Jurassic-aged fossil bird Archaeopteryx, from the Solnhofen Limestone of Germany, does have teeth. Unlike modern birds, Confuciusornis has three clawed fingers on the leading edge of each wing. Hundreds of specimens have been found, often in close proximity on bedding planes. These mass mortality beds consistent with the volcanic ash burial model that accounts for the exquisite preservation of Jehol fossils. Confuciusornis fossils frequently have well preserved wing, tail, body, and neck feathers. Some Confuciusornis specimens have exceedingly long tail feathers. Such long-tailed fossils are often found in close proximity to individuals having very short tail feathers. The Chinese have concluded that this may be evidence for sexual dimorphism in the species, and the long-tailed individuals are inferred to be males. The most distinctive skeletal feature is the presence of a large hole (fenestra) near the proximal end of the humerus of each arm.

This is a closeup of the skull (ventral view).

Classification: Animalia, Chordata, Vertebrata, Aves, Confuciusornithiformes, Confuciusornithidae

Stratigraphy: 3rd unit of the Yixian Formation (sensu Fürsich et al., 2007) (a.k.a. Jianshangou Unit; a.k.a. Jianshangou Bed; a.k.a. Chaomidianzi Formation), Jehol Group, Lower Cretaceous (an upper Upper Jurassic assignment was initially preferred by Chinese researchers, but available information indicates an Early Cretaceous age)

Locality: Sihetun Quarry, Liaoning Province, northeastern China

Birds are small to large, warm-blooded, egg-laying, feathered, bipedal vertebrates capable of powered flight (although some are secondarily flightless). Many scientists characterize birds as dinosaurs, but this is consequence of the physical structure of evolutionary diagrams. Birds aren’t dinosaurs. They’re birds. The logic & rationale that some use to justify statements such as “birds are dinosaurs” is the same logic & rationale that results in saying “vertebrates are echinoderms”. Well, no one says the latter. No one should say the former, either.

However, birds are evolutionarily derived from theropod dinosaurs. Birds first appeared in the Triassic or Jurassic, depending on which avian paleontologist you ask. They inhabit a wide variety of terrestrial and surface marine environments, and exhibit considerable variation in behaviors and diets.

References:

Wu et al. (2002) - Fossil Treasures from Liaoning. Beijing. Geological Publishing House. 138 pp. [in Chinese & English]

Chang et al. (2003) - The Jehol Biota. Shanghai. Shanghai Scientific & Technical Publishers. 209 pp.

Chen et al. (2005) - Jianshangou Bed of the Yixian Formation in West Liaoning, China. Science in China, Series D, Earth Sciences 48: 298-312.