Formation · Cretaceous
Yixian Formation (Jehol Biota)
Early Cretaceous unit, Liaoning · Hebei · Inner Mongolia
The Yixian and Jiufotang formations of Liaoning make up the Jehol Biota, the Early Cretaceous lake deposits that yielded feathered dinosaurs, early birds, mammals with fur, and the tiny fish Lycoptera on almost every shale slab. Lycoptera plates and Ephemeropsis mayfly nymphs are common in trade and were exported in bulk in the 1990s, but any vertebrate beyond those is subject to China's export ban and to intense fakery. Stratum flags Chinese provenance for the compliance gate.
| Country | China |
|---|---|
| Region | Liaoning, Hebei, Inner Mongolia |
| Age | Barremian, Early Cretaceous |
| Age range | ~130–120 Ma |
| Group | Jehol Group |
| PBDB collections | 214 collections, 1181 occurrences· Paleobiology Database |
Collecting and legality
China's Regulations on the Protection of Fossils (2011) prohibit export of vertebrate and other significant fossils without state approval; Lycoptera fish plates and insects have historically been tolerated, but feathered dinosaurs, birds and Psittacosaurus are seized at borders and returned. The Chinese market is also the world's largest source of fabricated composites ('Archaeoraptor' was one).
Lithology and setting
Lacustrine shales and volcanic tuffs of a rift-basin lake system, with ash falls that preserved feathers, fur and stomach contents.
Commonly recorded taxa (PBDB)
Genera most often recorded from this unit in the Paleobiology Database (first 200 occurrences): Confuciusornis (10), Psittacosaurus (10), Euenantiornithes (4), Apoclion (3), Czekanowskia (3), Ilerdocossus (3), Lycoptera (3), Manchurochelys (3), Monjurosuchus (3), Peipiaosteus (3), Pterodactyloidea (3), Sinornithosaurus (3), Sinosauropteryx (3), Sinoxytelus (3), Anura (2).
Source: Paleobiology Database
Elsewhere
Cite this article
Stratum Study. "Yixian Formation (Jehol Biota)" (Formation). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/formations/yixian-formation-jehol-biota. Accessed 2026-09-20.
@misc{stratum-yixian-formation-jehol-biota,
title = {Yixian Formation (Jehol Biota)},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/formations/yixian-formation-jehol-biota}},
year = {2026},
note = {Formation article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, pbdb, commons. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.