Ninety-seven-million-year-old magnetic fossils, left behind in North Atlantic sea beds by a mysterious, unknown creature, may provide evidence of a sort of biological GPS, according to new research.
If true, this would mark the earliest known creature to exhibit the magnetic geolocation sensing observed in modern birds and fish, called magnetoreception, which directs their migration patterns along Earth’s magnetic fields.
The researchers, an international team from the University of Cambridge and the Helmholtz-Zentrum Berlin, reported their findings in a paper published in Communications Earth & Environment, based on these minute fossil fragments.
Imaging Magnetism
For their work, the researchers created the first 3D images of the magnetic structure of these unique fossils. To make those images possible, one of the paper’s co-authors, Claire Donnelly at the Max Planck Institute in Germany, developed a new X-ray technique for the project to produce 3D magnetic images previously unattainable.
Those fossil images revealed a complex vortex in which magnetic properties were observed moving around a central line that cut through the fossil’s interior. Any minute changes in the magnetic field strength would produce a wobble in the particles, which the researchers believe allowed whatever creature they belonged to to map their journeys by magnetoreception.
“This magnetic particle not only detects latitude by sensing the tilt of Earth’s magnetic field but also measures its strength, which can change with longitude,” said lead author Richard J. Harrison.
One remarkable feature of the vortex is its stability. The team estimates that minor environmental disturbances that would typically interfere with navigation wouldn’t impact the magnetic particles.
“If nature developed a GPS, a particle that can be relied upon to navigate thousands of kilometres across the ocean, then it would be something like this,” Harrison added.
Magnetoreception
As a sense not directly experienced by humans, magnetoreception remains poorly understood by scientists. While the mechanism by which the faculty works is unclear, insects, birds, and fish have all been observed to employ it during their long journeys. By pushing back the origin of magnetoreception to such a remote period, the work offers new insight into how this feature may have evolved.
Although researchers are uncertain about how magnetoreception physically works, tiny magnetite crystals inside these creatures’ bodies acting as microscopic compasses is one solution put forth to explain the mystery.
Despite magnetoreception’s primary association with long-distance migrations, more subdued varieties exist. A primitive form of the sense is exhibited by some lake bacteria, which use it to swim to an optimal depth.
“At just 50–100 nanometres wide, these particles are the perfect compass needles,” said Harrison. “If you want to create the most efficient magnetic sense, smaller is better.”
The fossils in question may be tiny, but they eclipse the size of those lake bacteria’s magnetic particles by 10 to 20 times. Earlier research suggested that these fossils served as protective spines, but simulations indicated that they may contain a magnetic component. This strange magnetic possibility intrigued the team enough to prompt further research.
“It looks like this creature was carefully controlling the shape and structure of these fossils, and we wanted to know why,” Harrison said.
Magnetic Fossils
The magnetic fossils were unusual in that they do not resemble any particular creature; instead, they appear only in tiny bits shaped like bullets, needles, and spearheads. Researchers believe they are biological, but exactly what sort of creature left behind these scant traces remains a mystery.
“The next question is what made these fossils,” said Harrison. “This tells us we need to look for a migratory animal that was common enough in the oceans to leave abundant fossil remains.”
While the team has discerned what the fossils may have been used for, the identity of their owner remains a significant question for scientists. The team does have one suggestion for what the creature could have been: an early variety of eel.
In addition to possessing the same magnetoreception capabilities as fish, which govern the course of their spawning journeys, eels began appearing about 100 million years ago, and therefore fit the general time frame of the fossils. Additionally, in past research, scientists have detected magnetite particles within eels, although their small size has so far made it unfeasible to determine precisely where the magnetite resides within an eel’s body.
“Giant magnetofossils mark a key step in tracing how animals evolved basic bacterial magnetoreception into highly-specialised, GPS-like navigation systems,” Harrison said.
Although many questions remain, the team’s work, by harnessing a deeper understanding of the origins of magnetoreception, furthers scientists’ knowledge of nature’s mysterious magnetic sixth sense.
The paper, “Magnetic Vector Tomography Reveals Giant Magnetofossils are Optimised for Magnetointensity Reception,” appeared in Communications Earth & Environment on October 20, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.