University of Hamburg Researchers Help Identify Earliest Known Bryozoan Fossils from the Early Cambrian Period

Photo: UHH/Ernst

(IN BRIEF) An international research team involving the University of Hamburg has identified Early Cambrian bryozoan fossils for the first time, showing that these colonial animals existed around 520 million years ago. The fossils were discovered in the Xiannüdong Formation in China’s Shaanxi Province and include specimens of the known species Protomelission gatehousei as well as a newly identified species, Dayingomelission hexaclitia. The discovery is significant because bryozoans had not previously been confirmed from this early period, and the findings suggest that complex colonies made up of many individual organisms developed earlier than scientists had thought. The fossils were exceptionally well preserved, retaining not only skeletal structures but also mineralised soft tissues, including membrane-like features, spines and muscle fibres. By using modern imaging methods, the researchers were able to examine fine anatomical details that provide new evidence about the early evolution of colonial animal life. The findings, published in Nature, deepen scientific understanding of the Cambrian period, a time when many major animal groups emerged and life in the oceans diversified rapidly.

(PRESS RELEASE) HAMBURG, 4-Jun-2026 — /EuropaWire/ — An international team of researchers, including scientists from the University of Hamburg, has uncovered new fossil evidence that changes current understanding of when bryozoans first appeared in Earth’s history. The findings show that these colonial animals were already present during the Early Cambrian period around 520 million years ago, suggesting that complex animal colonies evolved earlier than previously recognised.

The study, published in Nature, focuses on exceptionally preserved bryozoan fossils from the Xiannüdong Formation in China’s Shaanxi Province. The discovery provides rare insight into a critical period in the evolution of animal life, when many major animal groups emerged and the oceans experienced a rapid expansion in biological diversity.

The Cambrian period, which began more than 500 million years ago, is widely associated with major evolutionary innovation. During this time, many animals developed hard body parts such as shells and skeletons, which improved their chances of being preserved as fossils. These remains continue to provide scientists with important evidence about how life on Earth became more complex.

Bryozoans are small invertebrate animals that still exist today, although modern forms differ from their ancient relatives. One of their defining features is their colonial way of life. Instead of living as isolated individuals, many microscopic organisms form a shared structure, often built from calcium carbonate, with individual members contributing to the function of the larger colony.

The research team, which included scientists from China, Sweden, Australia and Germany, examined fossils from the Xiannüdong Formation and identified specimens of the previously known bryozoan species Protomelission gatehousei. The team also described a newly identified species, Dayingomelission hexaclitia. Both organisms lived approximately 520 million years ago, making them the earliest confirmed bryozoan fossils from this period.

Until now, bryozoans had not been clearly documented from the Early Cambrian. The new findings indicate that the group appeared earlier and was more widely distributed during the Cambrian than scientists had previously assumed. The discovery also adds evidence to the study of coloniality, one of the important evolutionary developments in animal history.

Dr. Andrej Ernst, co-author of the study from the Department of Earth System Sciences at the University of Hamburg, said the findings show that bryozoans emerged earlier and were more widespread in the Cambrian period than previously believed. He noted that the research also provides new insight into the evolution of complex colonies, where many individuals live together and take on different roles within a shared biological structure.

The fossils are especially valuable because they preserved more than skeletal remains. Parts of the animals’ internal soft tissue were also retained after being mineralised by phosphate. This exceptional preservation allowed researchers to study anatomical features that are rarely visible in fossils of this age.

Using modern imaging techniques, the team identified fine structural details including membrane-like features, characteristic spines and individual muscle fibres. At the same time, the fossils displayed the modular skeletons associated with bryozoans, strengthening the evidence that these animals were already present in the Early Cambrian.

Dr. Ernst said the results suggest that bryozoans experienced significant evolutionary development during the Cambrian, much of which had remained hidden until recent fossil discoveries. Further finds from this period are expected to provide more information about the early evolution of animal life and the origins of complex biological organisation on Earth.

Media Contact:

Dr. Andrej Ernst
University of Hamburg
Faculty of Mathematics, Informatics and Natural Sciences
Department of Earth System Sciences
Tel: +49 40 2395-25018
Email: andrej.ernst@uni-hamburg.de

SOURCE: University of Hamburg