# Huajiying Formation

The Huajiying Formation is a geological formation in Hebei, People's Republic of China. Known for its fossils including feathered dinosaurs, the age of the formation is uncertain. It may represent an early portion of the Jehol Biota, dating to somewhere in the early Cretaceous or late Jurassic periods. It may correlate with the early Cretaceous Dadianzi Formation and parts of the Yixian Formation, with an age range between 140 and 122 Ma ago. It contains the Qiaotou Member, sometimes treated as a distinct formation.

## Age and stratigraphy

The Huajiying Formation contains the following members, in order from youngest to oldest:
* 5th Volcanic Member
* Guohedao Sedimentary Member
* 4th Volcanic Member
* Nianzigou Sedimentary Member
* 3rd Volcanic Member
* Qiaotou Sedimentary Member
* 2nd Volcanic Member
* Sichakou Sedimentary Member
* 1st Volcanic Member
The age of the formation is uncertain. Ji and colleagues suggested in 2008 that the Qiaotou Member correlates with the Dawangzhangzi bed of the Yixian Formation, dated to ~122 Ma ago by Zhou in 2006. Ji et al. also suggested that the lower Sichakou Member correlates with the Dadianzi Formation, dated to 140 Ma ago by Tian and colleagues in 2003.

## Paleobiota

The faunal lists below are based on a survey of the Huajiying Formation by Jin Fan and colleagues in 2008, unless otherwise noted.
| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. |

### Theropods

| Genus | Species | County | Member | Notes | Images |
| Archaeornithura | A. meemannae | Fengning | Sichakou Member | An ornithuromorph | Archaeornithura |
| Cruralispennia | C. multidonta | | Sichakou Member | An enantiornithine | Cruralispennia |
| Eopengornis | E. martini | | | An enantiornithine | |
| "Hebeiornis" | "H. fengningensis" | | Qiaotou Member | Nomen nudum/objective junior synonym of Vescornis |
| Jibeinia | J. luanhera | | Qiaotou Member | An enantiornithine |
| Jinfengopteryx | J. elegans | | Qiaotou Member | A troodontid | Jinfengopteryx |
| Protopteryx | P. fengningensis | | Sichakou Member | An enantiornithine |
| Shenqiornis | S. mengi | | Qiaotou Member | An enantiornithine |
| Vescornis | V. hebeiensis | | Qiaotou Member | An enantiornithine |
| Xunmenglong | X. yinlianglis | | | A compsognathid |

### Pterosaurs

| Genus | Species | County | Member | Abundance | Notes | Images |
| Cratonopterus | C. huabei | Fengning | | | A ctenochasmatid | |
| Ornithocheiroidea | Indeterminate | Fengning | | | Partial skeleton of an indeterminate ornithocheiroid | |

### Fishes

| Genus | Species | Abundance | Notes | Images |
| Lycoptera | L. davidi | Also present in the Jiufotang Formation & Yixian Formation | An osteoglossomorph | Lycoptera davidi Yanosteus longidorsalis |
| Lycoptera | L. tokunagai | | An osteoglossomorph | Lycoptera davidi Yanosteus longidorsalis |
| Peipiaosteus | P. fengningensis | | A fish related to sturgeons | Lycoptera davidi Yanosteus longidorsalis |
| Protopsephurus | P. liui | Also present in the Jiufotang & Yixian Formations | A paddlefish | Lycoptera davidi Yanosteus longidorsalis |
| Yanosteus | Y. longidorsalis | Also present in the Yixian Formation | A peipiaosteid | Lycoptera davidi Yanosteus longidorsalis |

### Invertebrates

| Genus | Species | County | Member | Abundance | Notes | Images |
| Yanjiestheria | Y. huajiyingensis | | | Well-preserved remains and eggs. | A spinicaudatan | |