Species: millenii XU, WANG & WU, 1999
Etymology: Millenii derived from Millennium, Latin for one-thousand years, referring to its discovery near the end of the twentieth century.

Holotype: IVPP V12811

Locality: Sihetun, Shangyuan, Beipaio City, Western Liaoning Province, China.

Horizon: Layer 6, Lower (Chaomidianzi) Yixian Formation, Jehol Group.

Biostratigraphy:

Age: Early Cretaceous.

Material: Crushed skull and fragmentary skeleton.
Note: Filamentous integument (Feathers?)

Referred material:

AZUMA, 2005

Locality: Western Liaoning Province, China.

Horizon: Yixian Formation, Jehol Group.

Biostratigraphy: Psittacosaurus Fauna, Confuciusornis Avifauna.

Age: Valanginian Stage, Upper Neocomian Subepoch, Early Early Cretaceous Epoch, Early Cretaceous.

Material:

IG-5b: Skull and skeleton with feather impressions.

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Sp

JI, NORELL, GAO, JI, & DONG, 2001

Locality: Fanzhangzi quarry, 20 km southwest of Lingyuan City, Liaoning Province, China.

Horizon:

Biostratigraphy:

Age: Early Jurassic.

Material:

NGMC 91 part and counterpart: Nearly complete specimen with ‘feathery’ integument and some claw sheaths.
Note: A Lycoptera near the left foot.

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XU, ZHOU, WANG, KUANG, ZHANG & DU, 2003

Locality: Chaoyang Basin, Liaoning Province, China.

Horizon:

Biostratigraphy:

Age: Early Cretaceous.

Material:

IVPP V13477: Fragmentary specimens with feathers.