A team of researchers from the Polish Geological Institute – National Research Institute and Jagiellonian University identified tracks in the Świętokrzyskie Mountains that may be the oldest known evidence of vertebrates attempting to move on land. These fossils, over 400 million years old, were left by lungfish—approximately 10 million years earlier than the first fully terrestrial four-legged animals (tetrapods) appeared.
The discovery was made by Dr. Piotr Szrek, Katarzyna Grygorczyk, Dr. Sylwester Salwa, Dr. Patrycja Dworczak, and Professor Alfred Uchman. The research results were published in the journal Scientific Reports.
Lungfish, represented today by a few species, are known as “living fossils.” They can move on land in search of water and bury themselves in sediment during dry periods, entering a state of dormancy. Fossils from the Early Devonian are extremely rare—the first fragments were found near Krzyżtopór Castle in Ujazd in 2016, which initiated long-term research. The most recent tracks, discovered between 2020 and 2021 in Ujazd and Kopiec, were exceptionally well-preserved due to a layer of volcanic ash that almost immediately covered the fresh prints.
The tracks, named Reptanichnus acutori (“crawling pioneer”), are not merely fin marks. They document a complex movement of the animal, including traces of the body being dragged along, impressions of the torso and tail, and distinct indentations left by the snout. The snout was used by the fish to “anchor” itself in the ground to pull the rest of its body forward. Experiments with living fish of the genus Protopterus showed an almost identical pattern of movement.
Notably, analyses revealed that the Devonian lungfish consistently pressed their snout into the sediment, tilting it to the left. The research team identified 35 such “left-turning” tracks, reperesenting the oldest known evidence of lateralization in vertebrates—that is, the dominance of one side of the body, similar to how humans typically prefer the right or left hand.
Source: Science in Poland
