What Was the First Animal to Move from Sea to Land?

For over a decade, scientists believed that a prehistoric millipede was the first creature to have made the transition from sea to land by beginning to breathe air.

Earlier this year, however, researchers studying fossils dug up from a quarry in Wisconsin in the 1980s took a closer look at the remains of two well-preserved scorpions. Measuring just one inch (2.5 cm) in length, Parioscorpio venator was roughly the same size as many modern scorpions. Most notably, these prehistoric scorpions were “likely breathing air” 437 million years ago, presumably after making the transition from life under water to life on terra firma.

The anatomy of these ancient arachnids, the scientists said, shows unmistakable evidence of circulatory, respiratory and digestive systems. The scorpions may not have been fully land-dwelling, though; they could have spent most of their time in the water but briefly emerged on land to mate.

Early landlubbers:

The first animals to venture onto land were likely primitive, prehistoric fish known as sarcopterygians, or lobe-finned fish. These fish had evolved sturdy fin structures that could support their weight in shallow water or mud, which eventually led to the development of limbs suitable for land travel.

According to fossil records, the transition from sea to land began in the late Devonian period, around 370 million years ago. This era witnessed the evolution of fish with features that would enable their descendants to live on land, marking a pivotal point in the history of life on Earth.

The transition from sea to land involved gradual adaptations over millions of years. Fish developed stronger fins that could function as proto-limbs, allowing them to navigate through shallow waters and eventually onto muddy banks. These adaptations were driven by environmental pressures and the opportunity to exploit new ecological niches.

To move from sea to land, animals needed several key adaptations: sturdy limbs for support and locomotion, lungs to breathe air, modified sensory systems for detecting stimuli in the air rather than water, and reproductive systems that did not rely on water for fertilization or the development of offspring.

While the exact species is not definitively known, Ichthyostega and Acanthostega are two of the earliest-known tetrapods that exhibit both aquatic and terrestrial features. These species represent some of the first vertebrates that could potentially have moved onto land, as evidenced by their fossilized remains.

The move from sea to land had a profound impact on evolution, leading to the diversification of life and the emergence of amphibians, reptiles, mammals, and eventually humans. This terrestrial colonization opened up vast new habitats and ecological opportunities, driving an explosion of adaptive radiation and complexity in life forms.