Ancient Reptile Footprints Challenge Theories on Land Animal Evolution Timing

Researchers in Australia have discovered the oldest known fossil footprint of reptile-like animals, dating back roughly 350 million years ago.

This discovery implies that the first animals began emerging from the oceans around 400 million years ago and adapted to terrestrial life much quicker than previously thought.

Stuart Smida, a paleontologist from California State University, remarked, “I believed the transition from fins to limbs took more time.”

Before this, the oldest known reptile footprints were found in Canada and dated to 318 million years ago.

The ancient footprints were uncovered in sandstone slabs near Melbourne, revealing reptile-like feet with elongated toes and claws.

Scientists estimate that the creature was about 2.5 feet long (80 cm) and might resemble a modern monitor lizard. These findings were published on Wednesday in the journal Nature.

Co-authors and paleontologists, including Arlberg from Uppsala University in Sweden, indicated that the evidence showcases the identification of nails surrounding the footprint.

“It’s a walking animal,” he stated.

Only animals that evolved to live entirely on land developed the claws seen in these fossils. Earlier vertebrates, such as fish and amphibians, did not have hard claws and depended on aquatic environments for laying eggs.

In contrast, branches of the evolutionary tree leading to modern reptiles, birds, and mammals, known as amniotes, developed feet equipped with claws suited for traversing dry ground.

Smida commented, “This is the earliest evidence we’ve encountered of animals with claws.”

During the time these ancient reptiles existed, the environment was warm and humid, with expansive forests beginning to take shape. Australia was then part of the supercontinent Gondwana.

The fossil footprints tell a story of a day in the life, Ahlberg explained. A reptile fled across the ground before light rain; some rain droplets lightly obscured the tracks. Subsequently, two more reptiles dashed in opposing directions before the ground hardened and became covered with sediment.

Co-author John Long, a paleontologist at Flinders University in Australia, stated: