Paulsepia mazonensis has captivated the scientific community as a cephalopod species first identified in 2000 from a remarkable 300-million-year-old specimen. This fascinating creature has earned a spot in the Guinness Book of World Records for being the world’s oldest octopus. Recent research has led to its reclassification as a distant relative of the nautilus, offering new insights into the timeline of octopus evolution, according to paleontologists.
Depiction of old cadmus collapse in the Mason Creek Basin, highlighting various Mason Creek fauna, including the polychaete Esconites zelus and the elasmobranch shark Bandringa rayi. Image credit: Franz Anthony.
Originally described from isolated siderite concretions, Paulsepia mazonensis has been recognized as the oldest known octopus, predating earlier estimates by over 150 million years. This revelation raises significant questions regarding our comprehension of cephalopod evolution, according to Dr. Thomas Clements, a paleontologist from the universities of Leicester and Reading.
This intriguing fossil from the Late Carboniferous Maisonkrieg Lagerstätte (311 to 360 million years ago) possesses distinct features, including a ‘sack-like’ fused head and mantle, symmetrical fins, and a pair of eyespots, alongside arms and specialized tentacles, yet lacks evidence for an inner or outer shell.
In a recent comprehensive study, researchers revisited this enigmatic fossil alongside several new specimens.
Employing advanced analytical methods, they uncovered a previously unrecognized radula, the toothed tongue characteristic of most molluscs.
Analysis of the alveolar bone suggests that Paulsepia mazonensis is more aligned with the shelled nautilus than previously thought.
This organism experienced significant decomposition prior to fossilization, leading to its ambiguous classification for decades.
“We conclude that Paulsepia mazonensis is synonymous with the Old Cadmus poli, based on morphological evidence,” the researchers confirmed.
This reinterpretation resolves a longstanding mystery regarding octopus evolution and unveils the oldest preserved nautilus soft tissue ever documented.
Through synchrotron micro-X-ray fluorescence elemental mapping, the team identified dental ossicles concealed within the concrete matrix of Paulsepia mazonensis.
The morphology of radial elements indicates that Paulsepia mazonensis does not correspond to coronal octamers but represents the oldest soft-tissue nautilus fossil discovered to date.
This reclassification challenges the Paleozoic origin of octopuses, further supporting a mid/late Mesozoic origin for crown octopuses while diminishing the credibility of the colloid affinity related to controversial Cambrian soft-bodied fossils like Nectocaris pterix.
The findings accentuate the complexities in interpreting exceptionally preserved soft tissue at the Masonkrieg Lagerstätte and underscore the necessity for thorough reevaluation of enigmatic consolidated soft-bodied fossil materials.
The team’s research paper has been published today in Proceedings of the Royal Society B.
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Thomas Clements et al. 2026. Synchrotron data reveals characteristics of nautiloids Paulsepia mazonensis refuting the Paleozoic origin of octopods. Proc Biol Sci 293 (2068): 20252369; doi: 10.1098/rspb.2025.2369
Source: www.sci.news
