Ancient ocean dwellers knew how to get food straight from the water

In other words, the Cambrian seas already had a way of eating that is still important in the oceans today: animals did not chase prey, but actually "filtered" the water.

Details

The researchers studied luolishanids, extinct marine animals from the lobopodia group. These were soft-bodied creatures that lived during the Cambrian period and looked very different from most modern animals.

The problem is that such organisms are poorly preserved in the fossil record. They didn't have hard shells or bones, so scientists have to work with rare well-preserved prints.

Previously, palaeontologists had already suggested that luolishanids may have fed on small organisms suspended in water. This was indicated by their front appendages, which were covered in fine, comb-like bristles.

In the new work, the researchers didn't just look at the shape of these appendages, but took measurements and performed statistical analyses. They examined the distance between the bristles and compared it to the animals' body size.

It turned out that the gaps between these "combs" were wider in larger individuals. This is similar to the patterns observed in modern marine filter-feeding animals: the size of the filter structures is related to the size of the prey and the animal itself.

This result supports the theory that loolishanids did catch food from the water - such as small plankton or other organic particles.

Why it matters

The finding helps us better understand how ancient marine ecosystems were organised after the Cambrian explosion - a period when the diversity of animal forms on Earth increased dramatically.

Luolishaniidae looked very unusual, but their way of eating turned out to be quite recognisable. Many marine invertebrates still use similar strategies: they pass water through special structures and retain their food.

This means that already more than 500 million years ago, ecological roles familiar to us from modern seas existed in the oceans. Some animals actively hunted, others crawled along the bottom, and some extracted food from the water column.

The study also shows that even the strangest animals of the Cambrian were not "evolutionary experiments without analogues". Many of them fit into understandable food chains and used strategies that proved successful for hundreds of millions of years.

Background

The Cambrian period began about 541 million years ago. This is when many new types of animals appeared in the oceans, including ancestors or distant relatives of modern groups.

Luolishaniidae belong to the lobopodia, extinct soft-bodied animals that can be related to lineages closely related to modern velvet worms and other invertebrates.

Their unusual bodies have long stumped scientists. But new methods of analysis allow not only to describe the appearance of such fossils, but also to draw conclusions about behaviour: how the animals moved, what they ate and what role they occupied in the ancient ecosystem.

Source

A study by Jared C. Richards and Javier Ortega-Hernández Predator-prey scaling laws support a suspension-feeding lifestyle in Cambrian luolishaniid lobopodians published in Biology Letters in 2026. The authors studied luolishaniid fossils and showed that the structure of their bristly anterior appendages is consistent with feeding on small organisms suspended in water.