Jehol Biota

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The Jehol Biota includes all the living organisms – the

The Yixian and Jiufotang Formations are considered Lagerstätte, meaning that they have exceptionally good conditions for fossil preservation. The fossils are numerous, but also very well preserved – often including articulated skeletons, soft tissues, colour patterns, stomach contents, and twigs with leaves and flowers still attached. Zhonghe Zhou et al.. (2003) deduced two things from this. The first is that the land animals and plants were washed into the lakes very gently, or were already in the lakes when they died. They do not show the damage seen in fossils formed by large floods. Secondly, volcanic ash is commonly inter-bedded with lake sediments, and ashfalls seem to have quickly buried the fossilized organisms, creating anoxic conditions around them and preventing scavenging.

Refuge and laboratory

Zhonghe Zhou et al. (2003) noted that, for the

The Jehol Biota includes many species that were previously known only from the

The Jehol Biota was not entirely isolated, however, because it also includes animals which were known from all around the world at the same time, including

Diversity

The Jehol Biota is particularly noteworthy for the very high diversity of fossils and the very large numbers of individuals of each species that have been recovered.

The Jehol Biota has produced fossils of plant macro- and

• gastropods: Bellamya
  clavilithiformis, B. fengtienensis, Probaicalia gerassimovi, P. spp., Viviparus, Galba, Hydrobia;
• bivalves
  : Arguniella cf. ventricosa (=Ferganoconcha linguanense)-Sphaerium (Sphaerium) anderssoni (=Sphaerium jeholensis) fossil group, Nakamuranaia, Weichangella;
• conchostracans
  : Eosestheria-Diestheria-Liaoningestheria or Eosestheria fossil group, Fengninggrapta, Yanjiestheria, Pseudestherites, Orthestheria;
• ostracods: Cypridea sulcata, C. vitimensis, C. yumenensis, C. koskulensis, C. tumescens-C. dunkeri-C. granulosa assemblage, C. (Yumenia) equimarginata, Limnocypridea tumulosa;
• insects: Ephemeropsis trisetalis, Mesolygaeus laiyangensis, Chironomaptera menlanura, Coptoclava longipoda, Clyptostemma xyphidle, Sinaeschuidia heishankouensis;
• fish: Lycoptera spp., Peipiaosteus, Sinamia, Haizhoulepis;
• reptiles: Monjurosuchus splendens (including Rhynchosaurus orientalis),^[6] Yabeinosaurus tenuis, Luanpingosaurus, Psittacosaurus;
• and mammals: Endotherium niinomi, Origolestes lii.^[7]

Study

The name "Jehol Biota" was first published by Gu (1962),

The Jehol group was defined by Gu (1962 and 1983) as a group of geological formations including the Jehol Coal-bearing Beds, the Jehol Oil Shale Beds, and the Jehol Volcanic Rocks.[11] By now the group includes, in ascending order, the Yixian Formation (including the Jingangshan, Tuhulu, Jianchang, Lower Volcanic and Volcanic Rock formations), the Jiufotang Formation (including the Shahai Formation) and the Fuxin Formation (including the Binggou, Haizhou and Upper Volcanic formations).^[12] Chiappe et al. argued in 1999 that the lower beds of the Yixian were best subdivided into a separate formation, the Chaomidianzi Formation, with a type locality at the village of Sihetun, approximately 25 km south of Beipiao City.^[13] However, this classification has fallen out of favor, and the Chaomidianzi Formation is disused as a synonym of the Jianshangou Bed of the Yixian Formation.^[14]

In 2008, Ji et al. argued that these traditional definitions of the Jehol Biota arbitrarily excluded earlier fossil beds that clearly represent the first evolutionary stages of the later faunas, even though lower beds also had representatives of Ephemeropsis and Lycoptera. They argued that the boundaries of the biota should rather be set based on the distinctive large-scale sequences of volcanism which produced the strata, with the upper boundary set at the Shahai and Fuxin formations and the lower boundary at the Zhangjiakou Formation. Along with this sedimentary correlation, they noted that the best index fossils to identify the biota are Peipiaosteus and Lycoptera. Under this definition, the earliest stage of the Jehol Biota is represented by the Huajiying Formation.^[5]

See also

• Daohugou Biota
• Jiufotang Formation
• Yixian Formation
  • Paleobiota of the Yixian Formation

References