Paraprotopteryx is a genus of enantiornithine bird. Though initially reported to be from the Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

 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...

, later investigation showed the fossil actually came from the Qiaotou member of the Huajiying Formation

Huajiying Formation

The Huajiying Formation is a geological formation in Hebei, People's Republic of China. Known for its fossils including primitive birds, the age of the ormation is uncertain. It may represent an early portion of the Jehol Biota, dating to somewhere in the early Cretaceous or late Jurassic periods...

 of Fengning, Hebei Province, 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 is therefore of uncertain age. The Huajiying Formation underlies the Yixian Formation, so the formation is either Early Cretaceous or Late Jurassic

Late Jurassic

The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

.

Distinguishing Characteristics

Paraprotopteryx has a furcula

Furcula

The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....

 (wishbone

Wishbone

Wishbone may refer to:* The wishbone, a Y-shaped bone found in birds* Wishbone suspension, an automobile suspension design.* Wishbone , an children's educational television show...

) which is shaped like a Y with a narrow angle between the clavicles. It also has an unusually shaped breastbone

Sternum

The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...

, distinguishing it from other birds in its suborder, the enantiornithines. The carpometacarpus

Carpometacarpus

The carpometacarpus is the fusion of the carpal and metacarpal bone, essentially a single fused bone between the wrist and the knuckles. It is a smallish bone in most birds, generally flattened and with a large hole in the middle. In flightless birds, however, its shape may be slightly different,...

 is only partially fused.

It has four long rectrices (flight feathers on the tail), which may represent an important step in feather evolution. For comparison, most modern birds have twelve rectrices; grouse

Grouse

Grouse are a group of birds from the order Galliformes. They are sometimes considered a family Tetraonidae, though the American Ornithologists' Union and many others include grouse as a subfamily Tetraoninae in the family Phasianidae...

 often have more than twelve, while grebes have none. In Paraprotopteryx they may have served as a secondary sex characteristic.