This has too many teeth. So it cannot be an octopus.
Durante más de veinte años, un pequeño fósil de Illinois fue considerado el pulpo más antiguo del mundo, un ancla en la comprensión de cómo evolucionaron los cefalópodos de ocho brazos. Ahora, gracias a una tecnología que permite ver dentro de la roca sin tocarla, los científicos han descubierto que la criatura nunca fue un pulpo: sus dientes la delatan como pariente del nautilo. La ciencia, fiel a su naturaleza, no borra el pasado, sino que lo reescribe con mayor precisión.
- Un fósil de 300 millones de años llamado Pohlsepia mazonensis perdió su título de pulpo más antiguo del mundo tras más de dos décadas de clasificación errónea.
- La brecha de 210 millones de años entre este espécimen y el siguiente fósil de pulpo conocido siempre fue inquietante, pero nadie la cuestionó formalmente hasta ahora.
- Usando un sincrotrón capaz de generar rayos más brillantes que el sol, los investigadores contaron once dientes por fila en la rádula del fósil, cuando los pulpos solo tienen entre siete y nueve.
- El patrón dental coincide con el de un nautiloide del mismo yacimiento, lo que sugiere que la criatura perdió su concha antes de fosilizarse y engañó a los paleontólogos durante generaciones.
- Guinness World Records suspendió el título original mientras revisa las nuevas evidencias, publicadas en los Proceedings of the Royal Society B.
- El Museo Field de Chicago, lejos de lamentar la corrección, ahora alberga el nautilo de tejido blando más antiguo jamás encontrado, un hallazgo potencialmente más valioso para la ciencia evolutiva.
Durante más de dos décadas, un pequeño fósil hallado en Mazon Creek, a unos ochenta kilómetros al suroeste de Chicago, ostentó un título extraordinario: el pulpo más antiguo del mundo, con 300 millones de años de antigüedad. La criatura, bautizada como Pohlsepia mazonensis, parecía empujar el origen de los pulpos modernos a un pasado casi inimaginable. El siguiente fósil de pulpo conocido tenía apenas noventa millones de años. Esa brecha de 210 millones de años debió haber generado preguntas inmediatas. En cambio, quedó suspendida en la literatura científica, aceptada pero incómoda.
Thomas Clements, zoólogo de la Universidad de Reading, decidió mirar más de cerca, literalmente dentro de la roca. Su equipo utilizó un sincrotrón, una máquina que acelera electrones a velocidades cercanas a la de la luz y produce haces de radiación más brillantes que el sol, para examinar el fósil sin dañarlo. Lo que encontraron fue una rádula, la estructura dentada que comparten muchos moluscos. Pero el conteo fue determinante: once dientes por fila. Los pulpos tienen entre siete y nueve. 'Tiene demasiados dientes', explicó Clements. 'No puede ser un pulpo.'
El patrón coincidía con el de otro fósil del mismo yacimiento, clasificado desde hace tiempo como nautiloide. La confusión original probablemente se debió a que Pohlsepia mazonensis perdió su concha antes de fosilizarse, dejando una masa ambigua que engañó a los investigadores durante generaciones. Guinness World Records suspendió el título mientras revisa las nuevas evidencias, publicadas en los Proceedings of the Royal Society B.
Para el Museo Field de Chicago, que custodia el espécimen, la corrección no es una pérdida sino un hallazgo distinto: el museo ahora posee el nautilo de tejido blando más antiguo jamás encontrado. La criatura que nunca fue un pulpo se ha convertido en algo más raro aún: una ventana hacia cómo la vida se organizaba cientos de millones de años antes de que el mundo moderno tomara forma.
For more than two decades, a small fossilized creature from Illinois held a remarkable distinction: it was the world's oldest known octopus, a 300-million-year-old specimen that rewrote the timeline of how eight-armed cephalopods evolved. Last week, scientists dismantled that claim entirely. The fossil, called Pohlsepia mazonensis, is not an octopus at all. It never was.
The creature was discovered in Mazon Creek, about fifty miles southwest of Chicago, in a region famous for preserving life from an era before dinosaurs walked the earth. When paleontologists identified it as an octopus in 2000, the finding seemed to push back the origins of modern octopuses by an almost incomprehensible span of time. The next-oldest known octopus fossil was only ninety million years old. That gap—210 million years—should have raised immediate questions. Instead, it lingered in the scientific literature, accepted but troubling.
Thomas Clements, a zoologist at the University of Reading and the lead researcher on the new study, understood the problem. "It's a very difficult fossil to interpret," he explained. When you look at the fossilized remains, they appear as little more than a whitish mass, roughly the size of a human hand. To someone studying octopuses, the shape suggested a deep-sea relative. But Clements and his team decided to look closer—literally inside the rock itself.
They used a synchrotron, a machine that accelerates electrons to near light-speed and generates beams brighter than the sun, to peer into the fossilized stone without damaging it. What they found was a row of tiny teeth, a structure called a radula that appears in many mollusks, including both octopuses and nautiluses. But the count was decisive: eleven teeth per row. Octopuses have seven or nine. "This has too many teeth," Clements said. "So it cannot be an octopus."
The tooth pattern matched another fossil from the same site, a creature called Paleocadmus pohli, which scientists had long classified as a nautiloid—a relative of the modern nautilus. The misidentification likely occurred because Pohlsepia mazonensis had decomposed and lost its characteristic shell before fossilizing, obscuring its true identity beneath layers of sediment and time. What remained looked ambiguous enough to fool researchers for more than two decades.
The findings, published this week in the Proceedings of the Royal Society B, prompted Guinness World Records to strip the fossil of its title. Adam Millward, the organization's managing editor, called the discovery "fascinating" and said they would suspend the original designation while reviewing the new evidence. The fossil's namesake, James Pohl, who discovered it, would have witnessed a quiet correction to the scientific record—the kind that rarely makes headlines but quietly reshapes how we understand the deep past.
For the Field Museum in Chicago, which houses the specimen, the reclassification is not a loss but a different kind of prize. Clements noted that the museum now possesses the oldest known soft-tissue nautilus ever found—a distinction that, for researchers studying cephalopod evolution, may be even more valuable than the title it surrendered. The creature that was never an octopus has become something rarer still: a window into how life organized itself hundreds of millions of years before the modern world took shape.
Notable Quotes
It's a very difficult fossil to interpret. When you look at it, it appears as a kind of white mass.— Thomas Clements, University of Reading
This has too many teeth, so it cannot be an octopus. The world's oldest octopus is actually a nautilus fossil, not an octopus.— Thomas Clements
The Hearth Conversation Another angle on the story
So scientists looked at this fossil for more than twenty years and got it completely wrong. How does that happen?
The fossil is genuinely ambiguous. It's a decomposed creature that lost its shell, so what's left is basically a blob of fossilized tissue. If you're trained to look for octopuses, your eye finds what it's looking for.
But they had technology to look inside it. Why didn't they use that earlier?
Synchrotrons are expensive and specialized. You don't use one on every fossil. You use it when something doesn't add up—and for a long time, nothing seemed to add up except the fossil itself.
The gap between this creature and the next-oldest octopus was 210 million years. Didn't that bother anyone?
It did. That's actually what prompted Clements to take another look. A gap that large is suspicious. It made people wonder if the original identification was wrong.
And the teeth gave it away.
Exactly. Eleven teeth per row instead of seven or nine. One small detail, but it's definitive. You can't argue with tooth count.
So now the Field Museum has the oldest soft-tissue nautilus instead of the oldest octopus.
Yes. And Clements is right—that might actually be more important. Soft tissue rarely survives fossilization. Having a 300-million-year-old nautilus with preserved tissue is extraordinarily rare.