Arthropods likely made honeycomb fossil not worms
A Pattern That Broke the Worm Hypothesis
For more than 150 years, the honeycomb-shaped pattern pressed into ancient marine sediments had a comfortable explanation. Soft, wormlike creatures made it. That explanation no longer holds up. A new analysis argues the geometry itself rules the worms out. Digging a sharp corner requires a rigid tool, and a soft body does not have one. The pattern, known as Paleodictyon, is probably the work of arthropods — the group that includes crabs, lobsters and the roly-poly. Andrea Baucon, a paleontologist at the University of Cagliari in Sardinia, Italy, puts the stakes plainly: “Our study addresses one of paleontology’s most enduring enigmas.” [1] The findings appear in Earth-Science Reviews, the peer-reviewed journal that published the analysis. [3]
The case rests on what a body can physically do. Wormlike creatures can only burrow where the ground is already weak. Arthropods carry rigid exoskeletons and jointed appendages — built for cutting precise angles into sediment. A hexagonal network with clean corners demands more than muscle. It demands mobility, efficient burrowing and spatial awareness. Those are cognitive skills that match what arthropods are known to do. Baucon and his colleagues ran no new laboratory experiments. They re-examined prior research and studied fossils both previously and newly discovered.
Among the newly discovered specimens is a 530-million-year-old Paleodictyon found in a quarry near Torre de Moncorvo, Portugal. [1] It ranks among the oldest specimens known. The timing matters. Paleodictyon enters the fossil record at roughly the same moment as the earliest fossil evidence of arthropods, in the early Cambrian Period, around 530 million years ago. Baucon is careful about what that coincidence means. It is not proof, he says. It is consistent with the team’s hypothesis.
The pattern has attracted famous eyes before. The Renaissance artist and inventor Leonardo da Vinci probably sketched Paleodictyon’s characteristic forms after seeing them in ancient marine sediments that now sit on dry land. The same shapes appear on seafloors today. In the 19th and 20th centuries, scientists blamed not only worms but also chemical processes and fossilized algae. The new work challenges the worm hypothesis directly and names arthropods — possibly a crustacean subgroup — as the likely creator.
A Skeptic Who Keeps the Case Open
Not everyone is ready to close the file. Stephen Hasiotis, a geologist at the University of Kansas in Lawrence, was not involved in the study. [2] He is not convinced arthropods are the sole creators. His objection is specific: “Without smoking gun evidence” spanning across geologic time and the various marine environments where the honeycombs have been found, other living things — including segmented worms — could still have made the formations, past and present. [2] Hasiotis does not dismiss the new hypothesis. He says it will doubtlessly push Paleodictyon aficionados “back onto the trail of whodunit and why.”
That push matters because the debate has never been settled. The pattern has been attributed to worms, to chemistry, to algae — three very different kinds of cause. Each attribution carried its own assumptions about what ancient seafloors allowed. The new study removes one assumption: that a soft body can carve a sharp corner. What remains is a question about the maker’s identity, not about the pattern’s geometry.
The disagreement between Baucon and Hasiotis is not about the fossils themselves. It is about what counts as sufficient evidence. Baucon’s team leans on the physical demands of the shape and the timing of the fossil record. Hasiotis asks for evidence from across time and across environments. Both positions leave the same question unresolved: no one has ever watched a Paleodictyon being built.
Where Artificial Intelligence Enters the Hunt
Baucon and his colleagues propose a way to end the waiting. They suggest researchers create Paleodictyon observatories — stations on ocean floors designed to catch the makers in action. The idea turns a fossil puzzle into a live surveillance problem. “Technologies such as artificial intelligence could help us automate the search for the creator of this mysterious structure,” Baucon says. [1] That is the next step the source names, and it is a different kind of science than the one that produced the hypothesis. It moves the question from rocks to real-time observation.
The intersection opens questions that neither the fossil record nor a single quarry can answer. If the maker still lives on modern seafloors, its digging behavior remains unobserved. If it does not, the conditions that once allowed it to carve sharp hexagons have shifted in ways the fossil record alone cannot show?