Caudipteryx

Caudipteryx (meaning "tail feather") is a genus of small oviraptorosaurian dinosaurs that lived in China during the Early Cretaceous, around 124.6 million years ago. They were feathered and extremely bird-like in their overall appearance, to the point that some paleontologists suggested it was a bird. Two species have been described: C. zoui (the type species), in 1998, and C. dongi, in 2000. Caudipteryx had a stout trunk, long legs, and was probably a swift runner. Its discovery has led to many intensive studies and debate over the relationship between birds and dinosaurs.

In 1997, several well-preserved dinosaur skeletons were recovered from the Jiulongsong Member of the Chaomidianzi Formation (now Jianshangou Bed of the Yixian Formation), at the Sihetun locality of Liaoning province, China. The fossils were later described in 1998 and used as the type specimens for the new dinosaur taxa Caudipteryx and Protarchaeopteryx. Caudipteryx was erected with the type species C. zoui and the holotype is NGMC 97-4-A, a nearly complete individual preserving conspicuous feather impressions and gastroliths. The paratype is NGMC 97-9-A, another relatively complete individual with feather impressions. The generic name, Caudipteryx, means "tail feather", and the specific name, zoui, is in honor of Zou Jiahua for his prominent support to the scientific community as the vice premier of China.

Around the summer of 1988, a partially complete skeleton of Caudipteryx lacking the skull was found in sediments of the "Layer 6" of the Yixian Formation, at the Zhangjiagou locality, which is set apart 3 km (1.9 mi) from Sihetun. This specimen, IVPP V 12344, was in 2000 described and designed as the holotype for new species Caudipteryx dongi, and in a similar fashion to previous specimens of the genus, it preserves exquisite traces of feather integument. The specific name dongi honors Zhiming Dong, a Chinese paleontologist.

During 2000, Zhong-He Zhou and colleagues described two additional specimens of Caudipteryx, BPM 0001 and IVPP V 12430, referred to C. zoui and C. sp. respectively. Both individuals preserve nearly complete skulls and have feather impressions. Further analyses to IVPP V 12430 have revealed the preservation of propatagium on its left arm.

In 2021 Xiaoting Zheng and team described STM4-3 representing an articulated individual lacking the skull and tail tip, including abundant integument, gastroliths, but also a cartilage fragment that was reported to preserve chondrocytes. The specimen was collected from outcrops of the Yixian Formation at Dapingfang Town near Chaoyang city, west Liaoning.

Caudipteryx was a small theropod, measuring 72.5–89 cm (2 ft 4.5 in – 2 ft 11.0 in) long and weighing about 5 kg (11 lb) based on femur length. Like many other maniraptorans, has a mix of reptile- and bird-like anatomical features.

It had a short, boxy skull with a beak-like snout that retained only a few tapered teeth in the front of the upper jaw.

Its short tail was stiffened toward the tip, with few vertebrae, like in birds and other oviraptorosaurs. It has a primitive pelvis and shoulder, and primitive skull details in the quadratojugal, squamosal, quadrate, jugal, and mandibular fenestra (in the cheek, jaw, and jaw joint). It has a hand skeleton with a reduced third finger, like that of early birds and the oviraptorid Heyuannia.