Earliest chitinozoans discovered in the Cambrian Duyun fauna of China

Chitinozoans are an enigmatic group of organic-walled marine microfossils with an abundant Lower Ordovician to Upper Devonian fossil record. They achieved maximum species diversity during the Middle Ordovician–Silurian, and their history during the group’s acme is well documented. Nevertheless, information about their origin and early evolution is sparse. Here we report three phosphatized flask-shaped vesicles recovered from the Cambrian Stage 5 (∼510 m.y. old) Duyun fauna of southern China as the earliest known chitinozoans, Eisenackitina? sp., extending the record of the microfossil group back by at least 20 m.y. Their exceptional occurrence within an Orsten-type Lagerstätte might imply a benthic mode of life. This discovery is significant in that it supplies critical data for evaluation of the basic morphology of Cambrian chitinozoans and assessment of their early evolution.