Paleodictyon\u00a0is a hexagonal, honeycomb-like network of burrows found in marine sediments going all the way back to the Cambrian, a geological period that began approximately 539 million years ago and lasted for about 52\u201355 million years.\u00a0<\/p>\n
This pattern is as widespread as it is mysterious, found everywhere from 3,500m depths on the Mid-Atlantic Ridge, to the mountain tops of the Italian Apennines. Leonardo da Vinci drew it around 1500 without even knowing what it was, and it was first described and named in 1850 by Giuseppe Meneghini.\u00a0<\/p>\n
It has persisted for more than half a billion years \u2013 and yet, its maker remained unknown for centuries.<\/p>\n
![\"\"](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/09\/ricerche-geopaleontologiche-in-Appennino-da-sx-Lo-Russo-Guerrini-Baucon-2048x1638-1.jpg\")
Geopalaeontological fieldwork in the Piacenza Apennines. From left: Andrea Baucon, Filippo Guerrini, Girolamo Lo Russo. Credit: Baucon et al.<\/p>\n
By investigating 50 fossils<\/a> spanning 530 million years, from Cambrian rocks in Portugal to the Italian Apennines, scientists have now identified the prime suspect: a small burrowing crustacean, a deep-sea cousin of the woodlouse<\/a>.<\/p>\n \u201cPaleodictyon\u00a0is one of the longest-running cold cases of palaeontology,\u201d says Andrea Baucon. \u201cThe fossils come from the Apennines, Portugal and Poland, while the morphometric analysis was carried out at the University of Cagliari. This approach allowed us to use the geometry of the traces to infer information about the organism that produced them.\u201d\u00a0<\/p>\n The oldest fossil used in the study was found in a quarry in northern Portugal.<\/p>\n \u201cThose burrows were produced 460 million years before T. rex,<\/a>\u201d adds Carlos Neto de Carvalho, co-author of the study. \u201cAnd something is still producing them today, thousands of metres deep, in total darkness.\u201d\u00a0<\/p>\n Solving the case<\/p>\n The researchers started with a hypothesis: the hexagonal structure is created by a marine arthropod<\/a>. Arthropods are known for creating straight tunnel segments, thanks to their jointed appendages and rigid exoskeletons, which also result in sharp directional changes.\u00a0<\/p>\n To confirm this hypothesis, the team worked through six lines of evidence: morphology (shape), stratigraphic distribution (when it appears in the rock record), environmental distribution (where it\u2019s found), taphonomy (how it\u2019s preserved), tracemaker attributes (what kind of animal could make it), and inferred function (what it was for).\u00a0<\/p>\n \u201cIt is a signature without an author,\u201d says Girolamo Lo Russo, co-author of the study. \u201cSince we cannot see the animal, we decided to let the geometry of the\u00a0Paleodictyon\u00a0speak.\u201d\u00a0<\/p>\n The researchers measured 1,314 points on fossil burrows housed at the\u00a0Natural History Museum of Piacenza<\/a>. They also headed out into the field to search for new fossil specimens, spending days on their knees, searching the Apennines and the Alps for any traces of the mysterious hexagon.\u00a0<\/p>\n \u201cAnyone walking in the Apennines is walking on an ancient ocean floor, uplifted in the building of that mountain chain,\u201d says Michelle Piazza, another co-author. \u201cThose rocks were deposited in the same environment where underwater vehicles now film\u00a0Paleodictyon\u00a0on muddy ocean floors. In this case, however, these are not fossils, but burrows recently excavated by living organisms.\u201d\u00a0<\/p>\n The researchers found that within a single hexagonal cell of the\u00a0Paleodictyon, the six sides differ by half a millimetre on average \u2013 a geometry very close to that of a regular hexagon. Rather than spreading any errors between cells, the animal that created the pattern corrected them locally, suggesting advanced orientation and measurement capabilities.\u00a0<\/p>\n These skills are compatible with the skills of the arthropod brain, though not exclusively. The first appearance of the\u00a0Paleodictyon\u00a0also coincides with the earliest fossil record of arthropods, which further supports the hypothesis.\u00a0<\/p>\n The remaining mystery\u00a0<\/p>\n These new findings are in no way the end of the\u00a0Paleodictyon\u00a0mystery \u2013 the research provides robust evidence supporting arthropods as the most plausible producers of the pattern, but Arthropoda is the largest animal phylum, with a number of species accounting for over 80 per cent of all known living animal species<\/a>.<\/p>\n The researchers point out some likely suspects within the phylum: peracarid crustaceans such as amphipods and isopods, particularly for the occurrences past the Ordovician period (about 485-443 million years ago).\u00a0<\/p>\n And another question remains: what is the\u00a0Paleodictyon\u00a0for? Whichever animal creates it, why does it do it? Until now, the leading hypothesis was that it might be used to farm bacteria inside the burrows.\u00a0<\/p>\n This study proposes another one. \u201cThe hexagonal mesh could work as the communication network of a colony, carrying chemical, hydraulic or acoustic signals,\u201d explains Andrea Barucci, co-author of the study.<\/p>\n The scientists note that further research is needed to address the remaining gaps in our understanding of this mysterious hexagonal pattern.<\/p>\n Photogrammetric video of Paleodictyon.\u00a0Credit: Baucon et al.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/09\/Paleodictyon-223c-3-2048x1638-1.jpg\"\/)
\u00a0Paleodictyon, Piacenza Apennines. Late Eocene (35 million years old). Credit: Baucon et al.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/09\/Paleodictyon-223c-2-2048x1638-1.jpg\"\/)
\u00a0Paleodictyon, Piacenza Apennines. Late Eocene (35 million years old). Credit: Baucon et al.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/09\/Paleodictyon-153-2048x1638-2.jpg\"\/)
\u00a0Paleodictyon, Piacenza Apennines. Late Eocene (35 million years old). Credit: Baucon et al.<\/p>\n