Benxi Area, Liaoning Chaetetes – coral reef. At the beginning of the Pennsylvanian, a massive south-north transgression occurred in this region. The sedimentary environment changed from fan delta to fiord coast and then into a carbonate platform, and thus several reefs with
a nearly east-west trend were built on the nearshore side of the platform. These reefs are relatively small, with thickness of 2–4 m. There are abundant benthic organisms found in these reefs, and the biotic content is up to 60% of the reef volume. Arachnastraea manchurica and
Chaetetes penchiensis are the dominant building organisms in these reefs. Their colonial skeletons are tabular in shape with varying thickness. Multithecopora penchiensis is the secondary building organism in the reefs of this region, and it mainly occur in the spaces between Chaetetes and Arachnastraea. There are also such binding organisms in the reef as Archaeolithoporella and Girvanella. The organisms associated with the Chaetetes coral reef are fusulinids, foraminiferans, brachiopods, ostracodas, bryozoans, gastropods and various genera of algae.