In a discovery that dramatically extends the known history of animal navigation, scientists have uncovered what appears to be the oldest direct evidence of creatures using Earth's magnetic field to orient themselves, dating back roughly 97 million years to the age of the dinosaurs, according to Space.com.

The findings, published by Nature, center on unusually large microscopic fossils preserved in deep-sea sediments from the Cretaceous period. These "magnetofossils," chains of magnetic crystals, bear the unmistakable structural signatures of the same biological compass that allows modern salmon, sea turtles and migratory birds to cross oceans with uncanny precision.

Until now, the earliest evidence of such magnetoreception dated to roughly 50 million years ago. The new fossils push that timeline back by nearly double and suggest the sensory ability arose far earlier in evolutionary history than previously thought.

"We can now say with confidence that some creature alive 97 million years ago possessed a functional magnetic sense capable of supporting accurate long-distance navigation," said Richard Harrison, a professor of earth sciences at the University of Cambridge and one of the study's lead authors.

However, the identity of this creature remains a mystery.

The breakthrough was made possible by an imaging technique called magnetic tomography, developed by Dr. Claire Donnelly, a physicist at the Max Planck Institute for Chemical Physics of Solids and a co-author of the study. Working at Britain's Diamond Light Source synchrotron, Donnelly used magnetic fields to map the orientation of tiny magnetic moments inside the fossils.

Traditional X-ray methods had failed to reveal the internal architecture because the crystals are encased in robust iron-rich shells. The new approach, akin to a magnetic version of a CT scan, revealed chains of magnetite particles arranged in ways that closely mirror the magnetoreceptor organs found in living animals.

"That we could resolve the internal magnetic structure at this scale was already remarkable," Donnelly said. "But to then recognize patterns consistent with navigational magnetoreception in 97-million-year-old fossils was truly thrilling.”

Although many animals are known to sense Earth's magnetic field, the underlying cellular mechanisms remain among biology's enduring puzzles. Some species appear to use crystals of magnetite as miniature compass needles while others may rely on light-sensitive chemical reactions in the eye.

"These giant magnetofossils represent a missing link," Harrison said. "They mark the point where simple bacterial magnetotaxis was transformed into the sophisticated internal GPS that allows animals to migrate across entire ocean basins today.”