Scientists are pushing back the date that the first land-walkers stepped foot on solid ground. Thanks to the discovery of prehistoric footprints from an 8-foot-long animal, scientists now say creatures strolled the Earth 20 million years earlier than previously thought. The prints were made by tetrapods—animals with backbones and four limbs—and could rewrite the history of when, where, and why fish evolved limbs and first walked onto land, the study says [National Geographic News]. The researchers published their results in the journal Nature.

Dozens of the fossilized footprints were found in an abandoned quarry in Poland, and the researchers say that the area was probably a lagoon or an intertidal flat when the tetrapod wandered across it about 395 million years ago. Researchers say the footprints in such old rock was a big surprise: They’re about 10 million years older than body fossils of creatures such as Tiktaalik and Panderichthys, … believed to represent the transition from lobe-finned fish to creatures fully adapted to life on land [Science News].

The tracks were made by several four-limbed creatures sporting prehistoric toes. There are distinct “hand” and “foot” prints, with no evidence of a dragging body or tail, because the animals’ body weight would have been partly supported by water [Guardian]. The results highlight how little scientists really know about the early history of land vertebrates, the researchers say, and the find pushes back the evolutionary fork where tetrapods split from fish. The discovery will force scientists to reexamine what they know about water-to-land transition during vertebrate evolution, say the study’s authors.

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Image: Per Ahlberg et al.